Methods For Providing Prophylactic Surface Treatment For Fluid Processing Systems And Components Thereof

ABSTRACT

In one embodiment, the invention relates to a method for creating a diffused thin film surface treatments on one or more interior surfaces of closed or partially closed fluid transport or processing systems providing improved surface prophylaxis against fouling. The method involves contacting the interior surfaces to be treated with a metal compound composition, and converting the metal compound composition to metal oxide for example by heating the surfaces to the desired temperature after all or a part of the system has been assembled. Embodiments of the present invention can be performed in situ on existing fluid processing or transport systems, which minimizes the disruption to the surface treatment created by welds, joints, flanges, and damage caused by or during the system assembly process.

RELATED APPLICATIONS

This application claims benefit of priority under PCT Chapter 1, Article8, and 35U.S.C. §119(e) of U.S. Provisional Application No. 60/851,354,entitled “METHOD FOR PROVIDING PROPHYLACTIC SURFACE TREATMENT FOR FLUIDPROCESSING SYSTEMS AND COMPONENTS THEREOF,” filed on Oct. 12, 2006,which is incorporated herein by reference.

TECHNICAL FIELD

The invention relates to methods for creating a metal oxide surfacetreatment on one or more surfaces of fluid transport or processingsystems providing improved surface prophylaxis against fouling. Themethods can be performed in situ on existing fluid processing ortransport systems, which minimizes the disruption to the surfacetreatment created by welds, joints, flanges, and damage caused by orduring the system assembly process. The invention also relates toarticles having one or more surfaces comprising at least one metaloxide.

BACKGROUND ART

Metals, ceramics, glasses, and cermets are used to construct manyfunctional items that are in turn used in carrying out industrialprocesses. Under certain operating conditions of these processes,surface degradation of a component can result from many causes. Thesecan include the corrosive nature of particular process conditions,thermal effects of the process or environment, contamination fromvarious elements becoming deposited on the surface or infiltrating intothe material, deposits formed by catalytic activity between thecomponent's material and the process fluid, galvanic activity betweenthe component's material and the process fluid, concentration cellcorrosion, crevice corrosion, graphitic corrosion, and a combination ofthese degradation mechanisms with each other or with other mechanisms.

During operation, various industrial process systems suffer degradationto the working sections of the system being attacked by variouschemicals and conditions. This occurs in the oil industry, colorantsindustry, cosmetics industry, food industry, pharmaceutical industry,chemical industry, and within closed systems such as cooling systems,heating and air conditioning systems, and many others. Additionalsystems that are affected by surface degradation are furnaces, boilers,internal combustion engines, gas turbine engine systems, rockets, etc.In any continuous or intermittent process system there is the risk ofsurface degradation due to the exposure of materials to certainchemicals and conditions. The surfaces exposed to the process maydegrade due to the material itself degrading, eroding, or corroding, orthe degradation may be in the form of deposits that accumulate on thematerial, affecting performance of one sort of another, e.g. flowefficiency through a pipe. Any kind of degradation is generally referredto as “fouling.” The typical solution to these types of fouling is toupgrade the material used to construct the functional item, be it apipe, a heat exchanger. etc. For example, a pipe may be constructed of anickel alloy stainless steel, rather than of common carbon steel, in anattempt to improve its inner and outer surface longevity and/orfunctionality. As another example, tanks used to hold various chemicalmaterials may experience material deposits or reactions on the innersurface of the tank, which can adversely affect the overall processefficiency. Coating or lining the interior of the tank with glass mayhelp to reduce these reactions because of the comparatively unreactivenature of the glass. In another example, a heat exchanger may be madefrom a high nickel content alloy to allow it to withstand hightemperature operation (as in the case of a hydrocarbon-fuel gas turbinesystem) while also reducing the amount of precipitates and deposits thatmight be occurring due to the caustic environment in which the heatexchanger is required to operate. In yet another example, an exhaustvalve for use in an internal combustion engine may be made from aparticular alloy in an effort to reduce the amount of carbon depositsforming on its surface; carbon deposits are a well known source ofoperational and emission problems for internal combustion engines.

Many industrial processes use materials to contain and transport variousfluids, slurries, or vapors, and those materials can become degradedduring use. These problems are known as “flow assurance” issues, whichis the industry term for the growth of flow restrictions in variouspipes, tubes, heat exchangers, and process containers, etc. Forinstance, the interior of a pipeline used in an industrial process mayhave its effective cross-sectional area reduced during operation bydeposits from the chemicals carried within the pipe during variousprocesses. In other cases, the vaporous or liquid elements carriedwithin a heat exchanger may precipitate the growth of crystallinedeposits if favorable conditions (temperature, pressure, presence ofcatalytic elements, etc.) exist within the system. In one example ofthis problem, crystals of various elements may grow during fluidprocessing operation because certain exposed molecules within thematerial surface of the interior of a conduit serve to catalyze thegrowth of some types of fibers on the interior wall of the conduit. Forexample, carbon fibers grow on the interior of metal pipes used forethylene transport, petro-chemical cracking tubes, petroleum refineryheaters, natural gas turbine blades, propane and LPG transport tanks,etc. While the mechanism of carbon fiber formation is not entirelyclear, it is believed that exposed iron or other atoms at the surface ofa steel or iron pipe in, e.g., a petroleum processing facility, may playa role in decomposing hydrocarbons flowing in the pipe into carbon.Because carbon has some solubility in iron, a steel or iron pipe mayabsorb this carbon. When the pipe material becomes saturated withcarbon, amorphous carbon fibers begin to grow rapidly at processtemperatures in the range of about 400° C. to about 800° C. Suchdeposits and/or fibrous growths affect the boundary layer development ofthe fluids and/or vapors passing through the pipe's interior, and cancause a significant restriction in the pipe's ability to transferfluids, vapors, or slurries. Furthermore, a corrosive environment,especially due to the presence of water and impurities or saltsdissolved in it, cause corrosion of metal pipes leading to eventualfailure. Also, it is known that petrochemical process fluids flowingthrough a metal tube at high temperature can cause metal wastage in whatis known as metal dusting, wherein the tube's inner surface is eroded byvarious mechanisms. Accordingly, there is a need in the art for a way toprevent or significantly inhibit the growth of carbon fibers while atthe same time inhibiting chemical attack of corrosive elements on thesubstrate, such as those that result in metal dusting of componentswithin a system.

All throughout industry, passageways and chambers regularly experiencedeposits on their interior surfaces caused by precipitates of theproduction fluids, deposits exacerbated by high temperatures,solidification of matter in slow moving boundary layers, and depositsoccurring by various other mechanisms. Some components, such as heatexchangers, can experience deposits from the processed fluid and fromthe heat exchange medium, thereby experiencing fouling on multipleinterior surfaces. In some cases, more than one interior surfacecontacts hydrocarbons being processed, such as in a heat exchanger thattransfers heat from processed material to feed material. Othercomponents, such as pipelines, can suffer corrosion on outer surfacesdue to process and/or environmental factors. The repairing of suchproblems has large costs associated with it due to interruption ofproduction while sections of a process system are identified and thencleaned, bypassed, and/or replaced. The petroleum industry, for example,has literally thousands of miles of connective pipelines, tubes,manifolds, as well as thousands of heat exchangers and process risers,etc. that require regular maintenance and repair at great costs to theindustry. For example, shutting down a petroleum refinery to repairand/or replace flow restricted pipes results in losses of approximately$200,000 to $500,000 per day of lost output.

In another example, at high process pressures and at temperatures above0° C., methane gas, present in the petrochemical stream may react withwater to form ice-like structures called hydrates. Hydrate formation inproduction-stream flow lines in the petroleum industry is also of greatconcern. Production-stream flow lines carry the raw, produced fluidsfrom the wellhead to a processing facility. If a flow line is operatedin the “hydrate region” (i.e., under conditions at which hydrates canform in an oil or gas wellstream), hydrates can deposit on the pipe'sinner wall and agglomerate until they completely block the flow line andstop the transport of hydrocarbons to the processing facility. Attemptsto prevent hydrate formation typically involve injecting additives intothe process fluid, but this can be a costly solution.

Because the problem of deposits on the interior of process pipes andtubes and the resulting reduction in flow is so large, there are anumber of industry associations participating in the study andimprovement of flow assurance in fluid processing systems. For example,the Gas Technology Institute estimates that the cost of hydrateformation remediation to industry is over $100 million per year.

Deposits on the interior surface of a pipe have significant negativeimpact on the pipe's ability to transfer fluids or gases, and theseresults can vary depending on the surface roughness of the deposit. Forexample, a smooth deposit of 5% on the interior of a pipe of circularcross-section can cause a loss of throughput of 10%, and require apressure increase of 30% to maintain constant flow. An uneven deposit of5% can increase the loss of throughput to 35% and require a pressureincrease of 140% to maintain constant flow. See Cordell, Introduction toPipeline Pigging, 5^(th) Edition (ISBN0-901360-33-3).

Deposit growth on the inside of a pipe can cause deposits or growths tobecome so large as to nearly stop all fluid flow through the pipe, asshown in FIG. 1. Conditions such as these can occur within a few months,or even within a few weeks of operation in the case of certainindustrial processes.

In other applications, scale is caused by precipitates formed within aprocess system's enclosures during oil and gas recovery, foodprocessing, water treatment, or other industrial processes. The mostcommon scales are inorganic salts such as barium sulphate, strontiumsulphate, and calcium carbonate. In some cases the scales may be partlyorganic (naphthenates, MEG-based etc.). Other scale formations may becomposed of sodium chloride, iron carbonate, and magnesium hydroxide.Scales formed from sulphates generally are due to mixing of chemicallyincompatible waters (like sea water and formation water). Carbonatescales result from pressure release of waters containing bicarbonate athigh concentration levels. Scaling degrades the process efficiency byplugging sand screens and production pipe, by causing failures invalves, pumps, heat exchangers, and separators. Scaling may also blocktransportation pipelines.

Furthermore, combustion buildup known as slag or scale often forms onthe flame-heated surfaces of furnaces, boilers, heater tubes,preheaters, and reheaters. The degree of combustion buildup depends onthe quality of the fuel being burned. Clean natural gas, for example,produces little or no combustion buildup, while coal, a “dirtier” fuel,produces significant combustion buildup. In particular, coal-fired powerplants experience significant combustion buildup on boiler vessels incontact with the coal combustion products. That buildup decreases heattransfer through the surface to the substance being heated, andtherefore wastes energy. Also, such combustion buildup increases theapplied temperature necessary to cause the substance to achieve adesired temperature. That increased temperature stresses the boilervessel, and may lead to material failure. Preventing combustion buildupon the flame-heated surfaces of a fluid transport or processing systemwould reduce energy consumption and extend equipment lifetime.

In some applications, the surfaces exposed to fluid flow may becomedegraded by the nature of the fluid itself, for example, in the case ofhydrogen transport and containment, which has the associated problem ofhydrogen embrittlement of the exposed materials.

Throughout industry and technology, sensors detect operationalparameters of various processes. By necessity, those sensors inhabit theprocess material, and are subject to those fouling mechanisms inherentin the processes they monitor. Unfortunately, even the smallest degreeof fouling may affect the accuracy of a sensor, even if that same degreeof fouling has only a negligible effect on the process itself. Often theremedy to sensor fouling is to design the sensor and sensor mountingapparatus to easily replace fouled sensors. Sensors represent high valuecomponents, and frequent sensor replacement adds significant costs inaddition to production loss due to shut down for sensor replacement.

The hydrocarbon process industry recognizes several distinct mechanismsfor the fouling of process components due to the unique conditions ofthose processes. One mechanism, known as coking, results from heatinghydrocarbons and driving off lighter, lower-boiling fractions causingthermal condensation of heavier fractions. Asphaltenes, tars, inorganicmaterial, and other solids will form on the surfaces of variouspetrochemical process units. In particular, vacuum columns, fluidcatalytic crackers, cokers, viscosity breakers, and any equipmenthandling heavier oil fractions at high temperatures suffer from thebuildup of coke. Also, the high-temperature environment of an ethylenecracker causes polymerization of carbon-carbon double bonds, the productof which condenses and forms coke upon further heating. When hightemperature plays a significant role and forms high molecular weightcoke, the resulting material is called pyrolytic coke. In a differentprocess, a metal species such as iron or nickel catalyses thedehydrogenation of a hydrocarbon, leading to what is known as catalyticcoking. Elemental carbon then deposits in the metal, weakening it. Whenthe system is shut down and cooled for decoking or other maintenance,the weakened metal can crack or spall. In some cases, the carburizedmetal can spall at process temperatures, resulting in metal dustingmentioned above.

In addition to reducing process throughput, coke buildup decreases heattransfer, requiring higher process temperatures consuming more energyand lowering equipment lifetime. Coke deposits can cause uneven heating,forcing the use of lower temperatures to avoid safety issues. Inaddition, shutting down those systems to decoke stops production. Systemshut downs and restarts cause thermal stress and increase the likelihoodof system malfunctions and material failure. Reducing coke buildup canextend equipment lifetime, improve process throughput, lower energyconsumption and operating temperatures, increase safety, and makesless-expensive alloys available for equipment construction. Moreover,increasing the actual temperature of the process stream (not just thetemperature of the outside of the heated vessels) would increase processefficiency and throughput. As it is, many process temperatures arelimited by the metallurgy of the heater tubes. Coke buildup requireshigher temperatures to be applied outside to obtain a given temperatureinside those tubes.

A second distinct mechanism for fouling equipment in the hydrocarbonindustry is corrosion by one or more chemicals present in the processstream. In particular, hydrogen sulfide (H₂S) attacks metal surfaces,causing the formation of iron sulfates that flake fromhydrocarbon-contacting surfaces, reducing the thickness and strength ofprocess equipment, clogging passages, and potentially diminishing theactivity of catalysts downstream. The presence of ammonia (NH₃),ammonium chloride (NH₄Cl), or hydrogen (H and H₂) enhances corrosiveattack by H₂S. Furthermore, acids such as hydrochloric acid (HCl),naphthenic acid, sulfuric acid (H₂SO₄), and hydrofluoric acid (HF) causecorrosive attack at various points in hydrocarbon processing systems.For example, naphthenic acid corrosion can be observed in processequipment handling diesel and heavier fractions, because naphthenicacids tend to have boiling points similar to diesel fractions. Corrosionby sulfuric acid and hydrofluoric acids occurs in alkylating units andassociated components employing those acids. Protection againstcorrosive mechanisms may be found in using chromium, nickel, andmolybdenum alloys, and by adding substances to the process stream suchas base to neutralize acid. Ironically, H₂S is added to process streamsto reduce metal dusting and other forms of fouling; yet H₂S itselfcauses corrosion. That compound also arises during hydrodesulfuringprocesses, when thiols and other naturally-present organosulfurcompounds react to form H₂S and desulfured hydrocarbons. In addition,metal systems handling alternative fuels such as alcohols includingmethanol and ethanol have been shown to experience corrosion. Protectingequipment against those corrosive mechanisms can lower operating costs,increase run length, extend equipment life, and make less-expensivematerials available for equipment construction.

As petroleum resources become less plentiful and more expensive,renewable sources of hydrocarbons increase in importance. Biodiesel, forexample, promises an alternative fuel to petrodiesel, the fuel derivedfrom crude oil. However, biodiesel refining presents unique challengesto refining equipment. Typically, a strong base such as sodium hydroxideor potassium hydroxide in alcohol digests triglycerides and long-chainfatty acids from a biological or renewable source, to form esterifiedfatty acids (biodiesel) and glycerin. That source may be corn, soy, oilpalm, pulp, bark, even restaurant waste and garbage. The harsh basicenvironment required for the digestion reaction may cause caustic stresscorrosion cracking, also known as caustic embrittlement. Heat treatmentsand nickel-based alloys may be necessary to avoid cracking, unless aless-expensive or more-effective means can be found to protect thatequipment.

Surfaces that become contaminated with debris during process operationoften adversely affect the efficiency and/or functionality of theprocess itself. Currently, most cleaning methods to remove deposits oninterior surfaces within systems of the types described above in processplants involve using one or more of the following strategies:

-   -   Chemical solvents such as kerosene or diesel fuel, or stronger        aromatic solvents such as xylene or toluene.    -   Dispersants that act as surfactants    -   Exothermic chemical reactions    -   Mechanical cleaning methods such as pigging or jetting    -   Thermal cleaning methods that involve hot oil or diesel fuel, or        the external application of high heat to break down surface        deposits

These methods involve considerable time and effort on the part ofprocess plant maintenance personnel, reducing output or throughput of asystem and causing the associated loss of revenue to the plant.

Similarly, in powder metal spraying operations, chemical attack occurswithin the spraying chamber that rapidly degrades its interior surfaces.In other applications such as food processing, beverage production, andsimilar closed process systems, material degradation on the interiorsurface of many portions of a process system occurs due to chemicalattack, material deposits, fibrous growth, and other surfacecontaminants.

Portions of fluid processing and transport systems exposed to theenvironment, especially those containing iron, also experience corrosionfrom environmental factors. Chemical, thermal, and galvanic attackrepresent leading mechanisms of exterior surface fouling in thosesystems.

There exists, therefore, the need for an improved means of protectingthe surfaces in many functional components from a variety ofcontaminants that build up or chemical erosion that occurs, throughvarious mechanisms, during the component's normal operation. An improvedsurface treatment that can be affordably applied and that provides ademonstrable resistance to surface contamination would serve to improvemany processes currently in use throughout industry. The inventiondisclosed herein addresses this need.

SUMMARY OF THE INVENTION

Various embodiments of the present invention are described herein. Theseembodiments are merely illustrations of the present invention. Numerousmodifications and adaptations thereof will be readily apparent to thoseskilled in the art without departing from the spirit and scope of theinvention.

The invention described herein provides a method for protecting surfacesof fluid transport or process equipment. As used herein, the term “fluidprocessing or transport system, or a component thereof” means anyequipment within which fluid (used herein to include any material thatis wholly or partially in a gaseous or liquid state, and includes,without limitation, liquids, gases, two-phase systems, semi-solidsystem, slurries, etc.) flows or is stored, such as pipes, tubes,conduits, heat exchangers, beds, tanks, reactors, nozzles, cyclones,silencers, combustion chambers, intake manifolds, exhaust manifolds,ports, etc., as well as any equipment within which a chemical orphysical change occurs, wherein at least one of the componentsparticipating in the chemical or physical change is a fluid. The methodof the invention protects the surfaces of such equipment by decreasingor preventing degradation, whether through deposition of material on thesurfaces, through infiltration of material into the surfaces, or throughcorrosive attack on the material surface. The method is adapted to beused, in some embodiments, on fluid process equipment, or portionsthereof, after assembly, resulting in significantly decreasedinterruption or interference with the protective functions of thecoating by welds, joints, or other structures within the equipment thatare created when the equipment is built or assembled.

The present invention relates, in some aspects, to forming at least onemetal oxide on an interior or exterior surface of fluid transport orprocess equipment. The at least one metal oxide can be formed on thesurface by (1) placing at least one metal compound on the surface and(2) converting at least some of the at least one metal compound into atleast one metal oxide. Metal compounds useful in the present inventioncontain at least one metal atom and at least one oxygen atom.Non-limiting examples of useful metal compounds include metalcarboxylates, metal alkoxides, and metal β-diketonates. Converting themetal compound can be accomplished by a wide variety of methods, suchas, for example, heating the environment around the metal compound,heating the substrate under the metal compound, heating the metalcompound itself, or a combination of those three. In other embodiments,converting the metal compound can be accomplished by catalysis.

Some embodiments of the present invention provide a method for formingat least one metal oxide on a surface of a fluid processing or transportsystem, or a component thereof, comprising: at least partiallyassembling the system; applying at least one metal compound to thesurface; and exposing the surface with the applied at least one metalcompound to an environment that will convert at least some of thecompound to at least one metal oxide. In other embodiments, the fluidprocessing or transport system is substantially assembled prior toforming at least one metal oxide coating on at least one surface of thesystem. In still other embodiments, the fluid processing or transportsystem is fully assembled prior to forming at least one metal oxidecoating on at least one surface of the system.

In some embodiments, the invention relates to a method for forming atleast one metal oxide on a surface of a fluid processing or transportsystem, or a component thereof, comprising: applying a metal compoundcomposition to the surface, wherein the metal compound compositioncomprises at least one metal salt of at least one carboxylic acid; andexposing the surface with the applied metal compound composition to anenvironment that will convert at least some of the salt to at least onemetal oxide.

In some embodiments, the invention relates to a method for forming atleast one metal oxide on a surface of a fluid processing or transportsystem, or a component thereof, comprising: applying a metal compoundcomposition to the surface, wherein the metal compound compositioncomprises at least one metal alkoxide; and exposing the surface with theapplied metal compound composition to an environment that will convertat least some of the metal alkoxide to at least one metal oxide.

In some embodiments, the invention relates to a method for forming atleast one metal oxide on a surface of a fluid processing or transportsystem, or a component thereof, comprising: applying a metal compoundcomposition to the surface, wherein the metal compound compositioncomprises at least one metal β-diketonate; and exposing the surface withthe applied metal compound composition to an environment that willconvert at least some of the metal β-diketonate to at least one metaloxide.

In further embodiments, the invention relates to a method for forming atleast one metal oxide on a surface of a fluid processing or transportsystem, or a component thereof, comprising: applying a metal compoundcomposition to the surface, wherein the metal compound compositioncomprises at least one rare earth metal compound, and at least onetransition metal compound; and exposing the surface with the appliedmetal compound composition to an environment that will convert at leastsome of the compounds to at least one metal oxide.

The invention, in additional embodiments, relates to a method forforming at least one metal oxide on a surface of a fluid processing ortransport system, or a component thereof, comprising:

applying a liquid metal compound composition to the surface, wherein theliquid metal compound composition comprises a solution of at least onerare earth metal compound and at least one transition metal compound, ina solvent, and

exposing the surface with the applied liquid compound to a heatedenvironment that will convert at least some of the metal compound to atleast one metal oxide, thereby forming a metal oxide coating on thesurface.

In some embodiments, the metal oxide coating may be crystalline,nanocrystalline, amorphous, thin film, or diffuse, or a combination ofany of the foregoing. For example, a metal oxide coating in someembodiments of the present invention may comprise a thin film thatcontains both nanocrystalline and amorphous regions.

In other embodiments, the invention relates to a method for forming anoxidizing coating on an interior surface of a fluid processing ortransport system, comprising:

applying a liquid metal carboxylate composition to the surface, whereinthe liquid metal carboxylate composition comprises a solution of atleast one rare earth metal salt of a carboxylic acid and at least onetransition metal salt of a carboxylic acid, in a solvent, and

exposing the surface with the applied liquid metal carboxylatecomposition to a heated environment that will convert at least some ofthe metal carboxylate to metal oxides, thereby forming a thin layer of ananocrystalline coating on the surface.

In some embodiments, the invention relates to a method for forming anoxidizing coating on an interior surface of a fluid processing ortransport system, comprising:

applying a liquid metal carboxylate composition to the surface, whereinthe liquid metal carboxylate composition comprises a solution ofzirconium carboxylate and at least one transition metal salt of acarboxylic acid, in a solvent, and

exposing the surface with the applied liquid metal carboxylatecomposition to a heated environment that will convert at least some ofthe metal carboxylate to metal oxides, thereby forming a thin layer of ananocrystalline coating on the surface.

In additional embodiments, the method of the invention further includesa step of applying a solution of organosiloxane-silica in ethanol overthe formed oxide coating and exposing the coated substrate to anenvironment that will remove volatile components from the solutionwithout decomposing organo-silicon bonds. In some embodiments, this stepcan be repeated once or more.

The various coatings of the present invention are formed, in someembodiments, by a method of forming an oxidizing coating on a substratecomprising:

-   -   (a) applying a liquid metal compound composition to the        substrate, wherein the liquid metal compound composition        comprises a solution of at least one rare earth metal compound        and at least one transition metal compound, in a solvent, and    -   (b) exposing the substrate with the applied liquid metal        compound composition to an environment that will convert at        least some of the metal compound to metal oxides, thereby        forming an oxidizing coating on the substrate.

In other embodiments, the invention relates to metal oxide coatings (andarticles coated therewith) containing two or more rare earth metaloxides and at least one transition metal oxide. Further embodiments ofthe invention relate to metal oxide coatings (and articles coatedtherewith), containing ceria, a second rare earth metal oxide, and atransition metal oxide. Some embodiments relate to metal oxide coatings(and articles coated therewith), containing yttria, zirconia, and asecond rare earth metal oxide. In some cases, the second rare earthmetal oxide can include platinum or other known catalytic elements.

In the case of catalytic surfaces, this method allows for cost savingsby reducing the bulk amount of the catalyst. And, it also allows a widervariety of catalysts to be applied either as mixtures or in disparatelayers to achieve tightly targeted results.

Therefore, some embodiments of the invention create a protective metaloxide coating on a chosen surface to serve as a prophylaxis againstattack from chemical, thermal, ionic, or electronic degradation. Themetal oxide coatings of some embodiments prevent the growth of fibers,formation of hydrate crystals, and act as a prophylaxis generallyagainst growth of any materials that block, interfere, or contaminatethe successful operation of an enclosed system.

Accordingly, some embodiments of the present invention provide a methodfor decreasing or preventing fouling of a surface of a fluid processingor transport system, or a component thereof, comprising applying atleast one metal compound to the surface, and exposing the surface withthe applied at least one metal compound to an environment that willconvert at least some of the compound to at least one metal oxide,wherein the at least one metal oxide is resistant to fouling.

Other embodiments of the present invention provide a method fordecreasing or preventing fouling of a surface of a sensor, or acomponent thereof, comprising applying at least one metal compound tothe surface, and exposing the surface with the applied at least onemetal compound to an environment that will convert at least some of thecompound to at least one metal oxide, wherein the at least one metaloxide is resistant to fouling.

Some embodiments of the present invention provide a method for reducingor preventing coke buildup on a surface of a fluid processing ortransport system, or a component thereof, comprising applying at leastone metal compound to the surface, and exposing the surface with theapplied at least one metal compound to an environment that will convertat least some of the compound to at least one metal oxide, wherein theat least one metal oxide is resistant to coke buildup.

Other embodiments of the present invention provide a method for reducingor preventing corrosive attack on a surface of a fluid processing ortransport system, or a component thereof, comprising applying at leastone metal compound to the surface. and exposing the surface with theapplied at least one metal compound to an environment that will convertat least some of the compound to at least one metal oxide, wherein theat least one metal oxide is resistant to corrosive attack.

Still other embodiments provide methods for reducing or preventingcombustion buildup on a flame-heated surface of a fluid processing ortransport system, or a component thereof, comprising: applying at leastone metal compound to the surface, and exposing the surface with theapplied at least one metal compound to an environment that will convertat least some of the compound to at least one metal oxide, wherein theat least one metal oxide is resistant to combustion buildup.

Further embodiments provide methods for reducing or preventing foulingof at least one metal surface of a combustion engine system or acomponent thereof, comprising applying at least one metal compound tothe surface, and exposing the surface with the applied at least onemetal compound to an environment that will convert at least some of thecompound to at least one metal oxide, wherein the at least one metaloxide is resistant to fouling.

Some embodiments of the invention provide an improvedcorrosion-resistant surface treatment through the creation of ananocrystalline grain structure of zirconia- or cerium-based materials,or surface treatments of other elemental compositions withnanocrystalline microstructures that serve to isolate the substrate fromchemical, thermal, or galvanic attack.

Additional embodiments provide a low cost means to form a useful coatingof zirconia- or ceria-based ceramic material on a substrate, the coatinghaving a nanocrystalline microstructure.

Some embodiments of the technology will prevent electrochemicalcorrosion by inhibiting the flow of electrons or ions into or from thesubstrate surface and from or into the process fluid stream.

Additional embodiments of the invention produce a dense metal oxidecoating that does not suffer from cracking due to thermal stresses.

Some embodiments produce a metal oxide coating that does not suffer fromcracking due to its fabrication method.

In further embodiments, the at least one metal oxide coating appearsuniform and without cracks or holes from about 100× to about 1000×magnification.

Some embodiments provide a metal oxide coating comprising only one metaloxide. Other embodiments provide a metal oxide coating comprising onlytwo metal oxides. Still other embodiments provide a metal oxide coatingcomprising only three metal oxides. In yet other embodiments, the metaloxide coating comprises four or more metal oxides.

The present invention, in some cases, also provides a low cost methodfor the creation of a metal oxide coating that serves to protect asurface from chemical, thermal, and/or galvanic attack. The presentinvention also provides a means to diffuse chosen surfaces with selectedchemical ingredients using a process that does not require damaging hightemperature cycles, in several embodiments.

Yet other embodiments of this invention provide corrosion resistantcoatings of organosiloxane-silica over metal oxide coating to impartprolonged usefulness to substrates, when such substrates have thetendency to corrode in aqueous environments with or without salts andother impurities dissolved in water.

Additional embodiments of the invention provide a means to form a metaloxide coating on the interior of a closed system after it is assembled,giving a prophylactic coating on all surfaces exposed to chosen processincluding welded areas, flanged joints, etc. Further embodiments providea fluid processing or transport system comprising at least one surfacecomprising at least one metal oxide coating, in which the system has alarge size.

Some embodiments of the invention may be implemented such that the metaloxide coatings are formed on components of a process system prior to itsassembly, for example, to a pipe or heat exchanger at its place oforiginal manufacture. In this manner, bulk coatings of metal oxides maybe formed in a more automated fashion in those embodiments, therebyproviding coverage over the majority of the interior of a system whilestill providing a reduced but chosen level of protection against surfacedegradation, i.e. leaving the in-field welded areas uncoated, which maybe suitable for some applications. in other embodiments, only certainsurfaces within a system may be coated for desired performance, whetherit be for surface protection against degradation, catalytic activity, ora combination thereof.

Accordingly, further embodiments of the present invention providearticles of manufacture adaptable to provide a surface of a fluidprocessing or transport system, or a component thereof, wherein thesurface comprises at least one metal oxide. In some of thoseembodiments, at least some of the at least one metal oxide is present ina diffused coating.

Further aspects, features and advantages of the present invention willbecome apparent from the drawings and detailed description of thepreferred embodiments that follow.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a photograph of a cross section of an untreated piperevealing crystalline growth that restricts flow through the pipe.

FIG. 2 shows a photograph of an uncoated steel coupon after a one hourexposure to Aqua Regia.

FIG. 3 shows a photograph of a steel coupon coated with “Zircon” afterone hour exposed to Aqua Regia.

FIG. 4 shows a photograph of a steel coupon coated with “Glass” afterone hour exposed to Aqua Regia.

FIG. 5 shows a photograph of a steel coupon coated with “YSZ” after onehour exposed to Aqua Regia.

FIG. 6 shows a photograph of a steel coupon coated with “Clay” after onehour exposed to Aqua Regia.

FIG. 7 shows TEM micrograph at 10,000× magnification of a steelsubstrate having a Y/Zr oxide coating in cross-section.

MODES FOR CARRYING OUT THE INVENTION

As used herein, the term “rare earth metal” includes those metals in thelanthanide series of the Periodic Table, including lanthanum. The term“transition metal” includes metals in Groups 3-12 of the Periodic Table(but excludes rare earth metals). The term “metal oxide” particularly asused in conjunction with the above terms includes any oxide that canform or be prepared from the metal, irrespective of whether it isnaturally occurring or not. The “metal” atoms of the metal oxides of thepresent invention are not necessarily limited to those elements thatreadily form metallic phases in the pure form. “Metal compounds” includesubstances such as molecules comprising at least one metal atom and atleast one oxygen atom. Metal compounds can be converted into metaloxides by exposure to a suitable environment for a suitable amount oftime.

As used herein, the term “phase deposition” includes any coating processonto a substrate that is subsequently followed by the exposure of thesubstrate and/or the coating material to an environment that causes aphase change in either the coating material, one or more components ofthe coating material, or of the substrate itself. A phase change may bea physical phase change, such as for example, a change from fluid tosolid, or from one crystal phase to another, or from amorphous tocrystalline or vice versa. “Adaptable to provide” indicates the abilityto make available. For example, an “article adaptable to provide asurface in a fluid processing or transport system” is an article, suchas a pipe, that has a surface that is or can be assembled into such asystem by using manufacturing, construction, and/or assembly steps.

The term alkyl, as used herein, refers to a saturated straight,branched, or cyclic hydrocarbon, or a combination thereof, typically ofC₁ to C₂₄, and specifically includes methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, t-butyl, n-pentyl, cyclopentyl, isopentyl, neopentyl,n-hexyl, isohexyl, cyclohexyl, 3-methylpentyl, 2,2-dimethylbutyl,2,3-dimethylbutyl, heptyl, octyl, nonyl, and decyl.

The term alkoxy, as used herein, refers to a saturated straight,branched, or cyclic hydrocarbon, or a combination thereof, typically ofC₁ to C₂₄, and specifically includes methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, t-butyl, n-pentyl, cyclopentyl, isopentyl, neopentyl,n-hexyl, isohexyl, cyclohexyl, 3-methylpentyl, 2,2-dimethylbutyl,2,3-dimethylbutyl, heptyl, octyl, nonyl, and decyl, in which thehydrocarbon contains a single-bonded oxygen atom that can bond to or isbonded to another atom or molecule.

The terms alkenyl and alkynyl, as used herein, refer to C₁ to C₂₄straight, branched, or cyclic hydrocarbon with at least one double ortriple bond, respectively.

The term aryl or aromatic, as used herein, refers to 5- to 12-memberedmonocyclic or bicyclic hydrocarbon ring molecule having conjugateddouble bonds about the ring. The ring may be unsubstituted orsubstituted having one or more alike or different independently-chosensubstituents, wherein the substituents are chosen from alkyl, alkenyl,alkynyl, alkoxy, hydroxyl, and amino radicals, and halogen atoms. Arylincludes, for example, unsubstituted or substituted phenyl andunsubstituted or substituted naphthyl.

The term heteroaryl as used herein refers to a five- to twelve-memberedmonocyclic or bicyclic aromatic hydrocarbon ring molecule having atleast one heteroatom chosen from O, N, P, and S as a member of the ring,and the ring is unsubstituted or substituted with one or more alike ordifferent substituents independently chosen from alkyl, alkenyl,alkynyl, hydroxyl, alkoxy, amino, alkylamino, dialkylamino, thiol,alkylthio, ═O, ═NH, ═PH, ═S, and halogen atoms.

The term hydrocarbon refers to molecules that contain carbon andhydrogen.

“Alike or different,” when describing three or more substituents forexample, indicates combinations in which (a) all substituents are alike,(b) all substituents are different, and (c) some substituents are alikebut different from other substituents.

Suitable metal compound precursors to form metal oxides includesubstances such as molecules containing at least one metal atom and atleast one oxygen atom. In some embodiments, metal compounds that formmetal oxides include metal carboxylates, metal alkoxides, and metalβ-diketonates.

A. Metal Carboxylates

The metal salts of carboxylic acids useful in the present invention canbe made from any suitable carboxylic acids according to methods known inthe art. For example, U.S. Pat. No. 5,952,769 to Budaragin disclosessuitable carboxylic acids and methods of making metal salts ofcarboxylic acids, among other places, at columns 5-6. The disclosure ofU.S. Pat. No. 5,952,769 is incorporated herein by reference. In someembodiments, the metal carboxylate can be chosen from metal salts of2-hexanoic acid. Moreover, suitable metal carboxylates can be purchasedfrom chemical supply companies. For example, cerium(III)2-ethylhexanoate, magnesium(II) stearate, manganese(II)cyclohexanebutyrate, and zinc(II) methacrylate are available fromSigma-Aldrich of St. Louis, Mo. See Aldrich Catalogue, 2005-2006.Additional metal carboxylates are available from, for example,Alfa-Aesar of Ward Hill, Mass.

The metal carboxylate composition, in some embodiments of the presentinvention, comprises one or more metal salts of one or more carboxylicacid (“metal carboxylate”). Metal carboxylates suitable for use in thepresent invention include at least one metal atom and at least onecarboxylate radical —OC(O)R bonded to the at least one metal atom. Asstated above, metal carboxylates can be produced by a variety of methodsknown to one skilled in the art. Non-limiting examples of methods forproducing the metal carboxylate are shown in the following reactionschemes:

nRCOOH+Me→(RCOO)Me^(n+)+0.5nH₂ (for alkaline earth metals, alkalimetals, and thallium).

nRCOOH+Me^(n+)(OH)_(n)→(RCOO)_(n)Me^(n+)+nH₂O (for practically allmetals having a solid hydroxide).

nRCOOH+Me^(n+)(CO₃)_(0.5n)→(RCOO)_(n)Me^(n+)+0.5nH₂O+0.5nCO₂ (foralkaline earth metals, alkali metals, and thallium).

nRCOOH+Me^(n+)(X)_(n/m)→(RCOO)_(n)Me^(n+)+n/mH_(m)X (liquid extraction,usable for practically all metals having solid salts).

In the foregoing reaction schemes, X is an anion having a negativecharge m, such as, e.g., halide anion, sulfate anion, carbonate anion,phosphate anion, among others; n is a positive integer; and Merepresents a metal atom.

R in the foregoing reaction schemes can be chosen from a wide variety ofradicals. Suitable carboxylic acids for use in making metal carboxylatesinclude, for example:

Monocarboxylic Acids:

Monocarboxylic acids where R is hydrogen or unbranched hydrocarbonradical, such as, for example, HCOOH-formic, CH₃COOH-acetic,CH₃CH₂COOH—propionic, CH₃CH₂CH₂COOH(C₄H₈O₂)-butyric, C₅H₁₀O₂-valeric,C₆H₁₂O₂-caproic, C₇H₁₄-enanthic; further: caprylic, pelargonic,undecanoic, dodecanoic, tridecylic, myristic, pentadecylic, palmitic,margaric, stearic, and nonadecylic acids:

Monocarboxylic acids where R is a branched hydrocarbon radical, such as,for example, (CH₃)₂CHCOOH-isobutyric, (CH₃)₂CHCH₂COOH—3-methylbutanoic,(CH₃)₃CCOOH-trimethylacetic, including VERSATIC 10 (trade name) which isa mixture of synthetic, saturated carboxylic acid isomers, derived froma highly-branched C₁₀ structure;

Monocarboxylic acids in which R is a branched or unbranched hydrocarbonradical containing one or more double bonds, such as, for example,CH₂═CHCOOH-acrylic, CH₃CH═CHCOOH-crotonic,CH₃(CH₂)₇CH═CH(CH₂)₇COOH-oleic, CH₃CH═CHCH═CHCOOH-hexa-2,4-dienoic,(CH₃)₂C═CHCH₂CH₂C(CH₃)═CHCOOH—3,7-dimethylocta-2,6-dienoic,CH₃(CH₂)₄CH═CHCH₂CH═CH(CH₂)₇COOH-linoleic, further: angelic, tiglic, andelaidic acids;

Monocarboxylic acids in which R is a branched or unbranched hydrocarbonradical containing one or more triple bonds, such as, for example,CH≡CCOOH-propiolic, CH₃C═CCOOH-tetrolic, CH₃(CH₂)₄C≡CCOOH-oct-2-ynoic,and stearolic acids;

Monocarboxylic acids in which R is a branched or unbranched hydrocarbonradical containing one or more double bonds and one or more triplebonds;

Monocarboxylic acids in which R is a branched or unbranched hydrocarbonradical containing one or more double bonds and one or more triple bondsand one or more aryl groups;

Monohydroxymonocarboxylic acids in which R is a branched or unbranchedhydrocarbon radical that contains one hydroxyl substituent, such as, forexample, HOCH₂COOH-glycolic, CH₃CHOHCOOH-lactic, C₆H₅CHOHCOOH-amygdalic,and 2-hydroxybutyric acids;

Dihydroxymonocarboxylic acids in which R is a branched or unbranchedhydrocarbon radical that contains two hydroxyl substituents, such as,for example, (HO)₂CHCOOH—2,2-dihydroxyacetic acid;

Dioxycarboxylic acids, in which R is a branched or unbranchedhydrocarbon radical that contains two oxygen atoms each bonded to twoadjacent carbon atoms, such as, for example, C₆H₃(OH)₂COOH-dihydroxybenzoic, C₆H₂(CH₃)(OH)₂COOH-orsellinic; further: caffeic, and pipericacids;

Aldehyde-carboxylic acids in which R is a branched or unbranchedhydrocarbon radical that contains one aldehyde group, such as, forexample, CHOCOOH—glyoxalic acid;

Keto-carboxylic acids in which R is a branched or unbranched hydrocarbonradical that contains one ketone group, such as, for example,CH₃COCOOH-pyruvic, CH₃COCH₂COOH-acetoacetic, andCH₃COCH₂CH₂COOH-levulinic acids;

Monoaromatic carboxylic acids, in which R is a branched or unbranchedhydrocarbon radical that contains one aryl substituent, such as, forexample, C₆H₅COOH—benzoic, C₆H₅CH₂COOH-phenylacetic,C₆H₅CH(CH₃)COOH—2-phenylpropanoic, C₆H₅CH═CHCOOH—3-phenylacrylic, andC₆H₅C≡CCOOH—3-phenyl-propiolic acids;

Multicarboxylic Acids:

Saturated dicarboxylic acids, in which R is a branched or unbranchedsaturated hydrocarbon radical that contains one carboxylic acid group,such as, for example, HOOC—COOH-oxalic, HOOC—CH₂—COOH-malonic,HOOC—(CH₂)₂—COOH succinic, HOOC—(CH₂)₃—COOH-glutaric,HOOC—(CH₂)₄—COOH-adipic; further: pimelic, suberic, azelaic, and sebacicacids;

Unsaturated dicarboxylic acids, in which R is a branched or unbranchedhydrocarbon radical that contains one carboxylic acid group and at leastone carbon-carbon multiple bond, such as, for example,HOOC—CH═CH—COOH-fumaric; further: maleic, citraconic, mesaconic, anditaconic acids;

Polybasic aromatic carboxylic acids, in which R is a branched orunbranched hydrocarbon radical that contains at least one aryl group andat least one carboxylic acid group, such as, for example,C₆H₄(COOH)₂-phthalic (isophthalic, terephthalic), andC₆H₃(COOH)₃-benzyl-tri-carboxylic acids;

Polybasic saturated carboxylic acids, in which R is a branched orunbranched hydrocarbon radical that contains at least one carboxylicacid group, such as, for example, ethylene diamine N,N′-diacetic acid,and ethylene diamine tetraacetic acid (EDTA);

Polybasic Oxyacids:

Polybasic oxyacids, in which R is a branched or unbranched hydrocarbonradical containing at least one hydroxyl substituent and at least onecarboxylic acid group, such as, for example, HOOC—CHOH—COOH-tartronic,HOOC—CHOH—CH₂—COOH-malic, HOOC—C(OH)═CH—COOH-oxaloacetic,HOOC—CHOH—CHOH—COOH-tartaric, and HOOC—CH₂—C(OH)COOH—CH₂COOH-citricacids.

In some embodiments, the monocarboxylic acid comprises one or morecarboxylic acids having the formula I below:

R—C(R″)(R′)—COOH  (I)

wherein:R is selected from H or C_(I) to C₂₋₄ alkyl groups; andR′ and R″ are each independently selected from H and C₁ to C₂₄ alkylgroups;wherein the alkyl groups of R, R′, and R″ are optionally andindependently substituted with one or more substituents, which are alikeor different, chosen from hydroxy, alkoxy, amino, and aryl radicals, andhalogen atoms.

Some suitable alpha branched carboxylic acids typically have an averagemolecular weight in the range 130 to 420. In some embodiments, thecarboxylic acids have an average molecular weight in the range 220 to270. The carboxylic acid may also be a mixture of tertiary andquaternary carboxylic acids of formula I. VIK acids can be used as well.See U.S. Pat. No. 5,952,769, at col. 6, 11, 12-51.

Either a single carboxylic acid or a mixture of carboxylic acids can beused to form the metal carboxylate composition. In some embodiments, amixture of carboxylic acids is used. In still other embodiments, themixture contains 2-ethylhexanoic acid where R is H, R″ is C₂H₅ and R′ isC₄H₉. In some embodiments, this acid is the lowest boiling acidconstituent in the mixture. When a mixture of metal carboxylates isused, the mixture has a broader evaporation temperature range, making itmore likely that the evaporation temperature of the mixture will overlapthe metal carboxylate decomposition temperature, allowing the formationof a solid metal oxide coating. Moreover, the possibility of using amixture of carboxylates avoids the need and expense of purifying anindividual carboxylic acid.

B. Metal Alkoxides

Metal alkoxides suitable for use in the present invention include atleast one metal atom and at least one alkoxide radical —OR² bonded tothe at least one metal atom. Such metal alkoxides include those offormula II:

M(OR²)_(z)  (II)

-   -   in which M is a metal atom of valence z+:    -   z is a positive integer, such as, for example, 1, 2, 3, 4, 5, 6,        7, and 8;    -   R² can be alike or different and are independently chosen from        unsubstituted and substituted alkyl, unsubstituted and        substituted alkenyl, unsubstituted and substituted alkynyl,        unsubstituted and substituted heteroaryl, and unsubstituted and        substituted aryl radicals,    -   wherein substituted alkyl, alkenyl, alkynyl, heteroaryl, and        aryl radicals are substituted with one or more alike or        different substituents independently chosen from halogen,        hydroxy, alkoxy, amino, heteroaryl, and aryl radicals.    -   In some embodiments, z is chosen from 2, 3, and 4.

Metal alkoxides are available from Alfa-Aesar and Gelest, Inc., ofMorrisville, Pa. Lanthanoid alkoxides such as those of Ce, Nd, Eu, Dy,and Er are sold by Kojundo Chemical Co., Saitama, Japan, as well asalkoxides of Al, Zr, and Hf, among others. See. e.g.http://www.kojundo.co.jp/English/Guide/material/lanthagen.html.

Examples of metal alkoxides useful in embodiments of the presentinvention include methoxides, ethoxides, propoxides, isopropoxides, andbutoxides and isomers thereof. The alkoxide substituents on a give metalatom are the same or different. Thus, for example, metal dimethoxidediethoxide, metal methoxide diisopropoxide t-butoxide, and similar metalalkoxides can be used. Suitable alkoxide substituents also may be chosenfrom:

-   -   1. Aliphatic series alcohols from methyl to dodecyl including        branched and isostructured.    -   2. Aromatic series alcohols: benzyl alcohol —C₆H₅CH₂OH;        phenyl-ethyl alcohol —C₈H₁₀O; phenyl-propyl alcohol —C₉H₁₂O, and        so on.

Metal alkoxides useful in the present invention can be made according tomany methods known in the art. One method includes converting the metalhalide to the metal alkoxide in the presence of the alcohol and itscorresponding base. For example:

MX_(z) +zHOR²→M(OR²)_(z) +zHX

in which M, R², and z are as defined above for formula II, and X is ahalide anion.

C. Metal β-Diketonates

Metal β-diketonates suitable for use in the present invention contain atleast one metal atom and at least one β-diketone of formula III as aligand:

-   -   in which    -   R³, R⁴, R⁵, and R⁶ are alike or different, and are independently        chosen from hydrogen, unsubstituted and substituted alkyl,        unsubstituted and substituted alkoxy, unsubstituted and        substituted alkenyl, unsubstituted and substituted alkynyl,        unsubstituted and substituted heteroaryl, unsubstituted and        substituted aryl, carboxylic acid groups, ester groups having        unsubstituted and substituted alkyl, and combinations thereof,    -   wherein substituted alkyl, alkoxy, alkenyl, alkynyl, heteroaryl,        and aryl radicals are substituted with one or more alike or        different substituents independently chosen from halogen atoms,        hydroxy, alkoxy, amino, heteroaryl, and aryl radicals.

It is understood that the β-diketone of formula III may assume differentisomeric and electronic configurations before and while chelated to themetal atom. For example, the free β-diketone may exhibit enolateisomerism. Also, the β-diketone may not retain strict carbon-oxygendouble bonds when the molecule is bound to the metal atom.

Examples of β-diketones useful in embodiments of the present inventioninclude acetylacetone, trifluoroacetylacetone, hexafluoroacetylacetone,2,2,6,6-tetramethyl-3,5-heptanedione,6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione, ethylacetoacetate, 2-methoxyethyl acetoacetate, benzoyltrifluoroacetone,pivaloyltrifluoroacetone, benzoyl-pyruvic acid, andmethyl-2,4-dioxo-4-phenylbutanoate.

Other ligands are possible on the metal β-diketonates useful in thepresent invention, such as, for example, alkoxides such as —OR² asdefined above, and dienyl radicals such as, for example,1,5-cyclooctadiene and norbornadiene.

Metal β-diketonates useful in the present invention can be madeaccording to any method known in the art. β-diketones are well known aschelating agents for metals, facilitating synthesis of the diketonatefrom readily available metal salts.

Metal β-diketonates are available from Alfa-Aesar and Gelest, Inc. Also,Strem Chemicals, Inc. of Newburyport, Mass., sells a wide variety ofmetal β-diketonates on the interne athttp://www.strem.com/code/template.ghedirect=cvdindex.

In some embodiments, the method of the invention can include apre-application cleaning step prior to the application of thecomposition. In these embodiments, the invention involves theapplication of one or more cleaning materials, which may be in vapor,liquid, semi-solid phase, or a combination of these to at least aportion of the surfaces of the final system, followed by a flushing anddrying cycle at a drying temperature. The cleaning technique can be ofthe type used for cleaning surfaces prior to coating, plating, painting,or similar surface treatments. The pre-application cleaning step mayalso include a pickling operation using known chemicals and process inorder to prepare the surface(s) for coating.

Some embodiments of the present invention provide a method fordecreasing or preventing fouling on a surface of a sensor, or acomponent thereof. Further embodiments provide a sensor comprising atleast one surface comprising at least one metal oxide. In still furtherembodiments, the at least one surface of the sensor comprises at leastone metal oxide, in which at least some of the at least one metal oxideis present in a diffused coating. Sensors may contain more than onepart, including but not limited to the sensing element(s), mountingstructures, and feedback means such as for example wiring which may bein protective cladding. Each of those parts have surfaces that maybenefit from a metal oxide coating; one or more of those surfaces can becoated in accordance with the invention. Sensors that appear inembodiments of the present invention include, but are not limited to,sight glasses, for example a sight glass on a boiler, thermocouples,resistance thermal devices (RTDs), pressure sensors, flow rate and massflow sensors, airspeed sensors, piezoelectric sensors, photo-opticcombustion sensors, high temperature chromatographs, optical sensors, UVsensors, infra red sensors, electromagnetic field sensors,electromagnetic wave sensors, radiation sensors, toxic chemical sensors,gas analyzers, oxygen sensors, nitrogen sensors, NO_(x) sensors, SO_(x)sensors, CO₂ sensors, CO sensors, diesel exhaust soot sensors, othersoot sensors, H₂S sensors, and humidity sensors, among others. Careshould be taken so that the applying of the at least one metal compoundand the converting to at least one metal oxide are accomplished tominimize or avoid damage to the sensor, or to avoid inhibiting sensoroperation. Damage can be minimized or avoided, in some embodiments, byconverting at a lower temperature, or without substantially heating thesurface. Alternatively, in other embodiments, non-sensing elementsurfaces can receive at least one metal oxide coating before the sensingelement(s) is/are assembled into the sensor.

Some embodiments of the present invention provide a metal oxide coatingon a surface that is subject to coke buildup. Such surfaces include, butare not limited to, one or more surfaces of:

the heaters, heat exchangers, vacuum tower, and pipes that contact theheavier fractions in a crude unit or a vacuum unit;the furnace, heater tubes, furnace outlets, and pipes of an ethylenecracker unit;the heaters, heater tubes, fractionator bottoms, stripper bottoms, heatexchangers, and pipes of a delayed coker unit or a viscosity breaker;the cyclone dip legs and stripper baffles of the reactor, the reactoroverhead line, the spent catalyst return line, the plenum of thecatalyst regenerator, and the bottom and lower trays of the fractionatorof a fluid catalytic cracking unit;the heaters, heater tubes, reactors, product pipes, catalyst transferpipes, and valves of a continuous catalytic reforming unit;the heaters, heater tubes, reactors, and pipes in a fixed bed catalyticreforming unit; andthe reactors, heaters, heat exchangers, and pipes of a syngas generationunit.

Other embodiments provide a metal oxide coating on a surface that issubject to corrosive attack by one or more species present in theprocess stream. Such surfaces include, but are not limited to, one ormore surfaces of:

the furnaces, towers, strippers, reheaters, heat exchangers, and pipesof a crude unit or a vacuum unit;the fractionators, strippers, compressors, heat exchangers, and pipes ofa delayed coker unit;a fractionator and pipes therefrom of a fluid catalytic cracking unit;on the knock-out drums, pipes, compressors, reheaters, and heatexchangers of a catalytic cracker's light ends recovery unit;the heat exchangers, product separators, debutanizer, overheadcondensers, overhead drums, and pipes of a continuous catalyticreforming unit;the reactors, stabilizers, accumulators, heat exchangers, and pipes of afixed bed catalytic reforming unit;the reactors, heaters, water washers, separators, hydrogen recyclecompressors, strippers, heat exchangers, pumps, and pipes of ahydrotreating, hydrodesulfuring, or hydrocracking unit;the trays, pipes, pumps, and bottoms of a sulfuric acid alkylation unit,including the outside surfaces of pipes that may be enclosed ininsulation;the settler, acid regenerator, acid vaporizer, fractionator, reboiler,strippers, condensers, recyclers, heat exchangers, defluorinators, KOHtreaters, pumps, and pipes of an HF or sulfuric acid alkylation unit;andthe reactor, separator, pumps, and pipes of a biodiesel refining unit.

The skilled artisan will appreciate that more than one mechanism canoperate to degrade the same surface. Accordingly, the foregoingembodiments do not suggest exclusive mechanisms for any given surface.

Still other embodiments of the present invention provide methods forreducing or preventing combustion buildup on a flame-heated surface of afluid processing or transport system, or a component thereof. Thatcombustion buildup can be any material that deposits on such surfaces,including, for example, slag, scale, coke, soot, and combinationsthereof. A flame-heated surface includes any surface exposed to fuelcombustion and its products, such as, for example, those surfacesexposed to the flame, smoke, soot, and/or fumes of combustion, even ifthat surface is not directly contacted by a flame. Such surfacesinclude, but are not limited to, insides of furnaces, preheaters,reheaters, and smoke stacks; outsides of boilers, heater tubes, andflame-heated reactors; as well as fuel conduits, valves, vents, burners,combustion control devices, ash conduits, and the like proximate to thecombustion area. A flame-heated surface does not necessarily includeprocess fluid-contacting surfaces. To illustrate, it is contemplatedthat heat is transferred from the flame-heated surface through thevessel wall to the process fluid-contacting surface. Thus, a vessel wallhas in general two surfaces, the flame-heated surface and the processfluid-contacting surface.

Further embodiments provide methods for reducing or preventing foulingof at least one metal surface of a combustion engine system, or acomponent thereof. Combustion engine systems include, but are notlimited to, internal combustion engines, two-stroke engines, four-strokeengines, gasoline engines, diesel engines, turboprop engines, jetengines, gas turbines, and rocket engines. Suitable metal surfacesinclude, but are not limited to, jet, turbojet, turbofan, ram jet, scramjet, and turbine engine surfaces including inlet, compressor, turbine,blades, recuperators, afterburner, nozzle, thrust vector surfaces, andfuel delivery components; internal combustion engine surfaces includingpistons, rotors, cylinders, housings, piston rings, seals, endplates,cylinder heads, valve heads, valve sterns, valve seats, valve faces,valve train components, cams, pushrods, cam followers, rocker arms,valve springs, valve guides, combustion chambers, crankcases, intakesystem components, supercharger components, exhaust manifolds, exhaustgas recirculation pipes and valves, turbocharger components, catalyticconverter components, exhaust pipes, fuel injectors, and fuel pumps; androcket engine surfaces including inlets, fuel delivery systems, fuelcombustion zones, and thrust vector surfaces. in some embodiments, themetal oxide coating of the metal surface of a combustion engine systemis an oxidizing coating. In further embodiments, the metal oxide coatingfurther comprises at least one metal. Metals that may be desired, suchas for catalytic purposes, for example, include but are not limited toplatinum, palladium, rhodium, nickel, cerium, gold, silver, zinc, lead,rhenium, ruthenium, and combinations of two or more thereof.

Still other embodiments provide a fluid processing or transport systemcomprising at least one surface comprising at least one metal oxidecoating, in which the system has a large size. A large size is usefulfor commercial scale processes. Industrial fluid processing or transportsystems include, but are not limited to, oil refineries; oil refinerysubsystems such as crude units, atmospheric units, vacuum units, delayedcokers, fluid catalytic crackers, fixed bed catalytic crackers,continuous catalytic reformers, naphtha reformers, hydrotreaters,hydrocrackers, alkylators including sulfuric acid alkylators and HFalkylators, amine treaters, sulfur recovery units, sour water strippers,isomerization units, and hydrogen reforming units; waste water treatmentplants; cooling water systems such as those found in manufacturingplants and power plants; desalinization plants; and processing systemsfound in colorants manufacturing, cosmetics manufacturing, foodprocessing, chemical manufacturing, pharmaceutical manufacturing, andthe like.

In some embodiments, the surface of the fluid processing or transportsystem to receive a metal oxide coating in accordance with the presentinvention has a surface area greater than about 100 square feet. Inother embodiments, the surface area ranges between about 100 square feetto about 500 square feet, between about 500 square feet to about 1,000square feet, between about 1,000 square feet to about 10,000 squarefeet, between about 10,000 square feet to about 20,000 square feet,between about 20,000 square feet to about 50,000 square feet, betweenabout 50,000 square feet to about 100,000 square feet, between about100,000 square feet to about 1,000,000 square feet, between about1,000,000 square feet to about 10,000,000 square feet, between about10,000,000 square feet to about 1 square mile, between about 1 squaremile to about 5 square miles, between about 5 square miles to about 10square miles, or greater than about 10 square miles.

The surface to be treated according to the invention also can bepretreated, in further embodiments, before the application of thecomposition. In some cases, the surface can be etched according to knownmethods, for example, with an acid wash comprising nitric acid,sulphuric acid, hydrochloric acid, phosphoric acid, or a combination oftwo or more thereof, or with a base wash comprising sodium hydroxide orpotassium hydroxide, for example. In further cases, the surface can bemechanically machined or polished, with or without the aid of one ormore chemical etching agents, abrasives, and polishing agents, to makethe surface either rougher or smoother. In still further cases, thesurface can be pretreated such as by carburizing, nitriding, painting,powder coating, plating, or anodizing. Thin films of chrome, tin, andother elements, alone or in combination, can be deposited, in someembodiments. Methods for depositing thin films are well known andinclude chemical vapor deposition, physical vapor deposition, molecularbeam epitaxy, plasma spraying, electroplating, ion impregnation, andothers.

In some embodiments of the present invention, a metal compound comprisesa transition metal atom. In other embodiments, a metal compoundcomprises a rare earth metal atom. In further embodiments, the metalcompound composition comprises a plurality of metal compounds. In someembodiments, a plurality of metal compounds comprises at least one rareearth metal compound and at least one transition metal compound. Metalcarboxylates, metal alkoxides, and metal β-diketonates can be chosen forsome embodiments of the present invention.

In further embodiments, a metal compound mixture comprises one metalcompound as its major component and one or more additional metalcompounds which may function as stabilizing additives. Stabilizingadditives, in some embodiments, comprise trivalent metal compounds.Trivalent metal compounds include, but are not limited to, chromium,iron, manganese, and nickel compounds. A metal compound composition, insome embodiments, comprises both cerium and chromium compounds.

In some embodiments, the metal compound that is the major component ofthe metal compound composition contains an amount of metal that rangesfrom about 65 to about 97% by weight or from about 80 to about 87% byweight of the total weight of metal in the composition. In otherembodiments, the amount of metal forming the major component of themetal compound composition ranges from about 90 to about 97% by weightof the total metal present in the composition. In still otherembodiments, the amount of metal forming the major component of themetal compound composition ranges from about 97 to about 100% by weightof the total metal present in the composition.

The metal compounds that may function as stabilizing additives, in someembodiments, may be present in amounts such that the total amount of themetal in metal compounds which are the stabilizing additives is at least3% by weight, relative to the total weight of the metal in the metalcompound composition. This can be achieved in some embodiments by usinga single stabilizing additive, or multiple stabilizing additives,provided that the total weight of the metal in the stabilizing additivesis greater than 3%. In other embodiments, the amount of the stabilizingmetal is less than 3% relative to the total weight of metal in the metalcompound composition. In yet other embodiments, the total weight of themetal in the stabilizing additives ranges from about 3% to about 35% byweight. In still other embodiments, the total weight for the metal inthe stabilizing additives ranges from about 3 to about 30% by weight,relative to the total weight of the metal in the metal compoundcomposition. In other embodiments, the total weight range for the metalin the stabilizing additives ranges from about 3 to about 10% by weight.In some embodiments, the total weight range for the metal in thestabilizing additives is from about 7 to about 8% by weight, relative tothe total weight of the metal in the metal compound composition. Stillother embodiments provide the stabilizing metal in an amount greaterthan about 35% by weight relative to the total weight of the metal inthe metal compound composition.

The amount of metal in the metal compound composition, according to someembodiments, ranges from about 20 to about 150 grams of metal perkilogram of metal compound composition. In other embodiments, the amountof metal in the metal compound composition ranges from about 30 to about50 grams of metal per kilogram of metal compound composition. In furtherembodiments, the metal compound composition can contain from about 30 toabout 40 grams of metal per kg of composition. Amounts of metal lessthan 20 grams of metal per kilogram of metal compound composition orgreater than about 150 grams of metal per kilogram of metal compoundcomposition also can be used.

The metal compound may be present in any suitable composition. Finelydivided powder, nanoparticles, solution, suspension, multi-phasecomposition, gel, vapor, aerosol, and paste, among others, are possible.

The metal compound composition may also include nanoparticles in thesize range of less than 100 nm in average size and being composed of avariety of elements or combination thereof, for example, Al₂O₃, CeO₂,Ce₂O₃, TiO₂, ZrO₂ and others. In some cases, the nanoparticles can bedispersed, agglomerated, or a mixture of dispersed and agglomeratednanoparticles. Nanoparticles may have a charge applied to them, negativeor positive, to aid dispersion. Moreover, dispersion agents, such asknown acids or surface modifying agents, may be used. The presence ofnanoparticles may decrease the porosity of the final coating: the levelof porosity will generally decrease with increasing quantity anddecreasing size of the included nanoparticles. Coating porosity can alsobe influenced by applying additional coating layers according to theprocess of the invention; porosity will generally decrease with anincreasing number of layers. In some embodiments the nanoparticles maybe first mixed with a liquid and then mixed with the compoundcomposition; this method provides a means to create a fine dispersion ina first liquid which retains its dispersion when mixed with a second, orthird liquid. For example, nanoparticles of chosen elements, oxides,molecules, or alloys may be dispersed into a first liquid and, after adesired quality of dispersion is achieved, the nanoparticles in thefirst liquid may be mixed with the liquid metal compound compositionprior to the exposure of the final composition to an environment thatwill convert at least a portion of the metal compound(s) into metaloxides. The result may be a more dense film with reduced porous sites.

The applying of the metal compound composition may be accomplished byvarious processes, including dipping, spraying, flushing, vapordeposition, printing, lithography, rolling, spin coating, brushing,swabbing (e.g., with an absorbent “pig” of fabric or other material thatcontains the metal compound composition and is drawn through theapparatus), pig train (in which the metal compound composition, trappedbetween two or more pigs, is pushed through a system by compressed air,for example), or any other means that allows the metal compoundcomposition to contact the desired portions of the surface to betreated. In this regard, the metal compound composition may be liquid,and may also comprise a solvent. The optional solvent may be anyhydrocarbon and mixtures thereof. In some embodiments, the solvent canbe chosen from carboxylic acids; toluene; benzene; alkanes, such as forexample, propane, butane, isobutene, hexane, heptane, octane, anddecane; alcohols, such as methanol, ethanol, n-propanol, isopropanol,n-butanol, and isobutanol; mineral spirits; β-diketones, such asacetylacetone; ketones such as acetone; high-paraffin, aromatichydrocarbons; and combinations of two or more of the foregoing. Someembodiments employ solvents that contain no water or water in traceamounts or greater, while other embodiments employ water as the solvent.In some embodiments, the metal compound composition further comprises atleast one carboxylic acid.

The metal compound composition can applied in some embodiments in whichthe composition has a temperature less than about 250° C. Thatcomposition also can be applied to the substrate in further embodimentsat a temperature less than about 50° C. In other embodiments, the liquidmetal compound composition is applied to the substrate at roomtemperature. In still other embodiments, that composition is applied ata temperature greater than about 250° C.

Following application, the at least one metal compound is at leastpartially converted to at least one metal oxide. In some embodiments theat least one metal compound is fully converted to at least one metaloxide.

Suitable environments for converting the at least one metal compoundinto at least one metal oxide include vacuum, partial vacuum,atmospheric pressure, high pressure equal to several atmospheres, highpressure equal to several hundred atmospheres, inert gases, and reactivegases such as gases comprising oxygen, including pure oxygen, air, dryair, and mixtures of oxygen in various ratios with one or more othergases such as nitrogen, carbon dioxide, helium, neon, and argon, as wellas hydrogen, mixtures of hydrogen in various ratios with one or moreother gases such as nitrogen, carbon dioxide, helium, neon, and argon,also other gases such as, for example, nitrogen, NH₃, hydrocarbons, H₂S,PH₃, each alone or in combination with various gases, and still othergases which may or may not be inert in the converting environment. Thatenvironment may be heated relative to ambient conditions, in someembodiments. In other embodiments, that environment may comprisereactive species that cause or catalyze the conversion of the metalcompound to the metal oxide, such as, for example, acid-catalyzedhydrolysis of metal alkoxides. In still other embodiments, the metalcompound is caused to convert to the metal oxide by the use of inductionheating or lasers, as explained below.

The conversion environment may be accomplished in a number of ways. Forexample, a conventional oven may be used to bring the coated substrateup to a temperature exceeding approximately 250° C. for a given periodof time. In some embodiments, the environment of the coated substrate isheated to a temperature exceeding about 400° C. but less than about 500°C. for a chosen period of time. In other embodiments, the environment ofthe coated substrate is heated to a temperature ranging from about 400°C. to about 650° C. In further embodiments, the environment is heated toa temperature ranging from about 400° C. to about 550° C. In stillfurther embodiments, the environment is heated to a temperature rangingfrom about 550° C. to about 650° C., from about 650° C. to about 800°C., or from about 800° C. to about 1000° C. Depending on the size of thecomponents and/or process equipment, pipes, etc., the time period may beextended such that sufficient conversion of a desired amount of themetal compound to metal oxides has been accomplished.

In some applications, the oxidation of the surface being treated is notdesired. In these cases, an inert atmosphere may be provided in theconversion environment to prevent such oxidation. In the case of heatingthe component in a conventional oven, a nitrogen or argon atmosphere canbe used, among other inert gases, to prevent or reduce the oxidation ofthe surface prior to or during the conversion process.

The conversion environment may also be created using induction heatingthrough means familiar to those skilled in the art of induction heating.Alternatively, the conversion environment may be provided using a laserapplied to the surface area for sufficient time to allow at least someof the metal compounds to convert to metal oxides. In otherapplications, the conversion environment may be created using aninfra-red light source which can reach sufficient temperatures toconvert at least some of the metal compounds to metal oxides. Someembodiments may employ a microwave emission device to cause at leastsome of the metal compound to convert. In the case of induction heating,microwave heating, lasers, and other heating methods that can producethe necessary heat levels in a short time, for example, within seconds,1 minute, 10 minutes, 20 minutes, 30 minutes, 40 minutes, or one hour.Accordingly, in some embodiments, the conversion environment can becreated without the use of an inert gaseous environment, thus enablingconversion to be done in open air, outside of a closed system due to thereduced time for undesirable compounds to develop on the material'ssurface in the presence of ambient air.

The gas above the metal compound on the surface can be heated, in someembodiments, to convert the metal compound to the metal oxide. Heatingcan be accomplished by introducing high temperature process gases, whichare fed through the assembled fluid transport or processing system,wherein the joints, welds, connections, and one or more interiorsurfaces of the fluid transport or processing system become covered witha protective thin film of the desired metal oxide(s). This hightemperature gas can be produced by a conventional oven, inductionheating coils, heat exchangers, industrial process furnaces, exothermicreactions, microwave emission, or other suitable heating method.

If there are elements of the assembled process system and components orsurfaces on which it is not desired to have nanocrystalline layerapplied (e.g. fluid beds, catalytic surfaces, etc.), these can betemporarily bypassed using known methods of piping, valves, ports, etc.during one or more steps of the method of the invention, be it duringthe application of a composition to the inner surfaces or during thehigh temperature conversion stage, or a combination thereof. Likewise,areas that are to be kept free of the coating of the invention can bemasked-off using known means prior to the application of the method'scomposition and its conversion using some heat or energy source.

In other applications, the metal compound composition may be applied tochosen areas of a component or system and an induction heating elementmay be passed proximate to the area of interest to create the conversionenvironment. In some applications, the inner surface of a component maynot be visible by line of sight, but an induction wand held proximate tothe inside or outside surfaces of the component may allow sufficientheat to be developed on the wetted surfaces being treated with the metalcompounds such that the desired oxides are formed by an indirect heatingmethod. This technique would also be possible using infra-red heatingfrom inside or outside of a component, flame heating, or other knownheating methods wherein the material of the component can be raised tothe desired temperature to ensure the conversion of the metal compoundsto oxides. Using this method of indirect heating may also be used with achosen atmosphere that may be provided proximate to the wetted surfacesof the pipe or component, such as an inert atmosphere made up of argon,as one example, which would serve to prevent undesirable oxides to formon the material surface being treated.

In other applications, multiple coats may be desired such that furtherprotection of the material's surface is provided. To reduce the timebetween applications of the coating of the invention, cooling methodsmay be used after each heating cycle to bring the surfaces to therequired temperatures prior to subsequent applications of the metalcompounds. Such cooling methods may be used that are known to the artsuch as water spraying, cold vapor purging through the interior of thesystem, evaporative cooling methods, and others.

Representative coating compositions that have been found to be suitablein embodiments of the present invention include, but are not limited to:

ZrO₂ for example, at 0-90 wt %

CeO₂ for example, at 0-90 wt %

CeO₂—ZrO₂ where CeO₂ is about 10-90 wt %

Y₂O₃ Yttria-stabilized Zirconia where Y is about 1-50% mol %

TiO₂ for example, at 0-90 wt %

Fe₂O₃ for example, at 0-90 wt %

NiO for example, at 0-90 wt %

Al₂O₃ for example, at 0-90 wt %

SiO₂

Y₂O₃

Cr₂O₃

Mo₂O₃

HfO₂

La₂O₃

Pr₂O₃

Nd₂O₃

Sm₂O₃

Eu₂O₃

Gd₂O₃

Tb₂O₃

Dy₂O₃

Ho₂O₃

Er₂O₃

Tm₂O₃

Yb₂O₃

Lu₂O₃

Mixtures of these compositions are also suitable for use in theinvention.

Oxides of the following elements also can be used in embodiments of thepresent invention: Lithium, Beryllium, Sodium, Magnesium, Aluminum,Silicon, Potassium, Calcium, Scandium, Titanium, Vanadium, Chromium,Manganese, Iron, Cobalt, Nickel, Copper, Zinc, Gallium, Germanium,Arsenic, Bromine, Rubidium, Strontium, Yttrium, Zirconium, Niobium,Molybdenum, Technetium, Ruthenium, Rhodium, Palladium, Antimony,Tellurium, Silver, Cadmium, Indium, Tin, Cesium, Barium, Lanthanum,Cerium, Praseodymium, Neodymium, Promethium, Samarium, Europium,Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium, Ytterbium,Lutetium, Hafnium, Tantalum, Tungsten, Rhenium, Osmium, Iridium,Platinum, Gold, Mercury, Thallium, Lead, Bismuth, Radium, Actinium,Thorium, Protactinium, Uranium, Neptunium, Plutonium, Americium, Curium,Berkelium, Californium, Einsteinium, Fermium, Mendelevium, Nobelium, andLawrencium. Oxides containing more than one of the foregoing elements,and oxides containing elements in addition to the foregoing elements,also can be used in embodiments of the present invention. For example,SrTiO₃ and MgAl₂O₄ are included. Those materials are likely to form atleast in small amounts when appropriate metal compounds are used,depending on the conditions of the conversion process. In someembodiments, the molar ratio of metal compounds deposited on the surfacecorresponds to the molar ratio of metal oxides after conversion.

The invention relates, in some embodiments, to diffused coatings andthin films (and articles coated therewith) containing at least one rareearth metal oxide, and at least one transition metal oxide. As usedherein, “diffused” means that metal oxide molecules, nanoparticles,nanocrystals, larger domains, or more than one of the foregoing, havepenetrated the substrate. The diffusion of metal oxides can range inconcentration from rare interstitial inclusions in the substrate, up tothe formation of materials that contain significant amounts of metaloxide. A thin film is understood to indicate a layer, no matter howthin, composed substantially of metal oxide. In some embodiments, a thinfilm has very little or no substrate material present, while in otherembodiments, a thin film comprises atoms, molecules, nanoparticles, orlarger domains of substrate ingredients. In some embodiments, it may bepossible to distinguish between diffused portions and thin films. Inother embodiments, a gradient may exist in which it becomes difficult toobserve a boundary between the diffused coating and the thin film.Furthermore, some embodiments may exhibit only one of a diffused coatingand a thin film. Still other embodiments include thin films in which oneor more species have migrated from the substrate into the thin film. Theterms “metal oxide coating” and “surface comprises at least one metaloxide” include all of those possibilities, including diffused coatings,thin films, stacked thin films, and combinations thereof.

As explained herein, the diffused coating of some embodiments of theinvention provides increased performance, in part, because it penetratesthe surface of the coated substrate to a depth providing a firm anchorto the material being coated without the need for intermediate bondinglayers. In some embodiments, the diffused coating penetrates thesubstrate to a depth of less than about 100 Angstroms. In otherembodiments, the diffused coating penetrates from about 100 Angstroms toabout 200 Angstroms, from about 200 Angstroms to about 400 Angstroms,from about 400 Angstroms to about 600 Angstroms, and greater than about600 Angstroms, and in some embodiments from about 200 to about 600Angstroms. This diffused coating allows much thinner films [in someembodiments around 0.1 to 1 microns in thickness (or about 0.5 micronswhen approximately 6 layers are used)] to be applied, and yet mayprovide equivalent protection to that provided by conventional coatingor thin film technologies. This, in turn, allows for thinner films orcoatings to be established, reducing significantly the cost of materialsattaching to the substrate. Thus, some embodiments of the presentinvention provide a thin film no thicker than about 5 nm. Otherembodiments provide a thin film no thicker than about 10 nm. Still otherembodiments provide a thin film no thicker than about 20 nm. Still otherembodiments provide a thin film no thicker than about 100 nm. Otherembodiments provide a thin film having a thickness less than about 25microns. Still other embodiments provide a thin film having a thicknessless than about 20 microns. Still other embodiments provide a thin filmhaving a thickness less than about 10 microns. Yet other embodimentsprovide a thin film having a thickness less than about 5 microns. Someembodiments provide a thin film having a thickness less than about 2.5microns. Even other embodiments provide a thin film having a thicknessless than about 1 micron.

In some embodiments of the invention, the metal oxide coating cancontain other species, such as, for example, species that have migratedfrom the substrate into the metal oxide coating. In other embodiments,those other species can come from the atmosphere in which the at leastone metal compound is converted. For example, the conversion can beperformed in an environment in which other species are provided viaknown vapor deposition methods. Still other embodiments provide otherspecies present in or derived from the at least one metal compound orthe composition comprising the compound. Suitable other species includemetal atoms, metal compounds including those metal atoms, such asoxides, carbides, nitrides, sulfides, phosphides, and mixtures thereof,and the like. The inclusion of other species can be accomplished bycontrolling the conditions during conversion, such as the use of achosen atmosphere during the heat conversion process, for example, apartial vacuum or atmosphere containing O₂, N₂, NH₃, one or morehydrocarbons, H₂S, alkylthiols, PH₃, or a combination thereof.

Some embodiments of the present invention provide metal oxide coatingsthat are substantially free of other species. For example, small amountsof carbides may form along side oxides when, for example, metalcarboxylates are converted, if no special measures are taken toeliminate the carbon from the carboxylate ligands. Thus, convertingmetal compounds in the presence of oxygen gas, air, or oxygen mixed withother gases reduces or eliminates carbide formation in some embodimentsof the present invention. Also, rapid heating of the conversionenvironment, such as, for example, by induction heating, microwaveheating, lasers, and other heating methods that can produce thenecessary heat levels in a short time, reduces or eliminates formationof other species, in other embodiments. At least one rapid heatingtechnique is used in combination with an oxygen-containing atmosphere instill other embodiments.

Additional embodiments employ various heating steps to reduce oreliminate the formation of other species. For example, carbide formationcan be lessened during metal oxide formation in some embodiments byapplying a metal compound precursor composition containing a metalcarboxylate to a surface, subjecting the surface to a low-temperaturebake at about 250° C. under a vacuum, introducing air and maintainingthe temperature, and then increasing the temperature to about 420° C.under vacuum or inert atmosphere to convert the metal carboxylate intothe metal oxide. Without wanting to be bound by theory, it is believedthat the low-temperature bake drives off most or all of the carboxylateligand, resulting in an oxide film substantially free of metal carbide.

Still other embodiments employ more than one layer to achieve at leastone layer substantially without other species. For example, in someembodiments, a base coat of at least one metal oxide is formed from atleast one metal carboxylate under an inert atmosphere. Such a base coatmay contain metal carbides due to the initial presence of thecarboxylate ligands. Moreover, such a base coat may exhibit goodadhesion and strength, for example, when the surface comprises a carbonsteel alloy. Then, one or more subsequent metal compounds are repeatedlyapplied and converted in an oxygen-containing atmosphere, for example,and the subsequent layers of metal oxide form substantially withoutmetal carbides. In some embodiments, six or more layers are formed onthe base coat.

In addition, the effect of any mismatches in physical, chemical, orcrystallographic properties (particularly with regard to differences inthermal expansion coefficients) may be minimized by the use of muchthinner coating materials and the resulting films. Furthermore, thesmaller crystallite structure of the film (3-6 nanometers, in someembodiments) increases Hall-Petch strength in the film's structuresignificantly.

In some embodiments, the present invention provides methods of reducingdifferences in coefficients of thermal expansion between a substrate anda metal oxide coating proximal to the substrate. In some embodiments,methods of reducing differences in coefficients of thermal expansionbetween a substrate and at least one metal oxide comprise interposing adiffused coating between the substrate and the metal oxide. Interposingsuch a diffused coating comprises applying at least one metal compoundto the substrate, and then at least partially converting the at leastone metal compound to at least one metal oxide.

The thermal stability of the metal oxide coating can be tested, in someembodiments, by exposing the coated material to thermal shock. Forexample, a surface having a metal oxide coating can be observed, such asby microscopy. Then the surface can be exposed to a thermal shock, suchas by rapid heating or by rapid cooling. Rapid cooling can be caused by,for example, dunking the room-temperature or hotter surface into liquidnitrogen, maintaining the surface under liquid nitrogen for a time, andthen removing the surface from the liquid nitrogen. The surface is thenobserved again, to look for signs that the metal oxide coating isdelaminating, cracking, or otherwise degrading because of the thermalshock. The thermal shock test can be repeated to see how many shockcycles a given metal oxide coating can withstand before a given degreeof degradation, if any, is observed. Thus, in some embodiments of thepresent invention, the at least one metal oxide coating withstands atleast one, at least five, at least ten, at least twenty-five, at leastfifty, or at least one hundred thermal shock cycles from roomtemperature to liquid nitrogen temperature.

The nanocrystalline grains resulting from some embodiments of themethods of the present invention have an average size, or diameter, ofless than about 50 nm. In some embodiments, nanocrystalline grains ofmetal oxide have an average size ranging from about 1 nm to about 40 nmor from about 5 nm to about 30 nm. In another embodiment,nanocrystalline grains have an average size ranging from about 10 nm toabout 25 nm. In further embodiments, nanocrystalline grains have anaverage size of less than about 10 nm, or less than about 5 nm.

In other embodiments, the invention relates to metal oxide coatings(whether diffused, thin film, or both diffused and thin film) andarticles comprising such coatings, in which the coatings contain two ormore rare earth metal oxides and at least one transition metal oxide.Further embodiments of the invention relate to metal oxide coatings (andarticles comprising them), containing ceria, a second rare earth metaloxide, and a transition metal oxide. Some embodiments relate to metaloxide coatings (and articles comprising them), containing yttria,zirconia, and a second rare earth metal oxide. In some cases, the secondrare earth metal oxide can include platinum or other known catalyticelements.

In some embodiments, the metal compound applied to the surface comprisesa cerium compound, and the metal oxide coating comprises cerium oxide(or ceria). In other embodiments, the metal compound applied to thesurface comprises a zirconium compound, and the metal oxide coatingcomprises zirconia. In yet other embodiments, a solution comprising botha cerium compound and a zirconium compound is applied, and the resultingmetal oxide coating comprises ceria and zirconia. In some cases, thezirconia formed by the process of the invention comprises crystal grainshaving an average size of about 3-9 nm, and the ceria formed by theprocess of the invention comprises crystal grains having an average sizeof about 9-18 nm. The nanostructured zirconia can be stabilized in someembodiments with yttria or other stabilizing species alone or incombination. In still other embodiments, the metal oxide coatingcomprises zirconia, yttria, or alumina, each alone or in combinationwith one or both of the others.

In additional embodiments, the method of the invention further includesa step of applying an organosiloxane-silica composition over the formedoxide coating and exposing the coaled substrate to an environment thatwill remove volatile components from the composition without decomposingorgano-silicon bonds. Moreover, other treatments can be performed afterthe formation of an oxide coating. As explained herein, additional metaloxide coatings, which can be the same or different, can be added. Insome embodiments, the metal oxide(s) can be etched, polished,carburized, nitrided, painted, powder coated, plated, or anodized. Insome embodiments, the at least one metal oxide serves as a bond coat forat least one additional coating. Such additional coatings need not beformed according to the present invention. Some embodiments provide ametal oxide bond coat that allows an additional coating that would notadhere to the surface as well in the absence of the bond coat. Inaddition, the substrate can be subjected to a thermal treatment, eitherbefore or after a metal oxide coating is formed on the substrate. Forexample, a substrate having a metal oxide coating in accordance with thepresent invention can be annealed at high temperature to strengthen thesubstrate. In another example, a substrate can be held near absolutezero before or after a metal oxide coating is formed on the substrate.Suitable temperatures for thermal treatment range from nearly 0 K toseveral thousand K, and include liquid hydrogen, liquid helium, liquidneon, liquid argon, liquid krypton, liquid xenon, liquid radon, liquidnitrogen, liquid oxygen, liquid air, and solid carbon dioxidetemperatures, and temperatures obtained by mixtures, azeotropes, andvapors of those and other materials.

The methods of the present invention can be used during or aftermanufacturing a given component of a fluid processing or transportsystem. For example, one or more oxide coatings can be applied to a pipesection as it is manufactured, or after the pipe is assembled into afluid processing or transport system. Moreover, in some embodiments, themethods of the present invention can be incorporated into conventionalmanufacturing steps. For example, after pipes are welded, often they aresubjected to a heat treatment to relieve the stresses introduced by thewelding process. In some embodiments of the present invention, at leastone metal compound is applied after welding and before that heattreatment. In those embodiments, that one heat treatment converts atleast one metal compound into at least one metal oxide and relieveswelding-induced stresses.

The process of the invention may permit the use of coatings on a widevariety of materials, including application of CeO₂ and ZrO₂ coatings toceramics and/or solid metals previously not thought possible of beingcoated with these materials. Some embodiments of the present inventionprovide a relatively low temperature process that does not damage ordistort many substrates, does not produce toxic or corrosive watermaterials, and can be done on site, or “in the field” without theprocurement of expensive capital equipment.

Additionally, the nature of the resulting interstitial boundaries of theinvention's nanocrystalline structures in various embodiments can becomprised of chosen ingredients so as to increase ionic conductivitywhile decreasing electron conductivity, or can be comprised of choseningredients so as to increase the material's mixed conductivity, or tomodify its porosity. In a similar fashion, many other properties may bealtered through the judicious selection of various ingredients that areformulated as part of the metal compound composition of the invention.

In some embodiments of the present invention, a substrate whichcomprises at least a portion of a component's structure is placed withina vacuum chamber, and the chamber is evacuated. Optionally, thesubstrate can be heated or cooled, for example, with gas introduced intothe chamber or by heat transfer fluid flowing through the substratemounting structure. If a gas is introduced, care should be taken that itwill not alter the substrate in an unintended manner, such as byoxidation of a hot iron-containing surface by an oxygen-containing gas.Introduced gas optionally can be evacuated once the substrate achievesthe desired temperature. Vapor of one or more metal compounds, such ascerium(IV) 2-hexanoate, enters the vacuum chamber and deposits on thesubstrate. A specific volume of a fluid composition containing the metalcompound can provide a specific amount of compound to the surface of thesubstrate within the vacuum chamber, depending on the size of thechamber and other factors. Optionally, a chosen gas is vented into thechamber and fills the vacuum chamber to a chosen pressure, in oneexample, equal to one atmosphere. The chamber is heated to a temperaturesufficient to convert at least some of the compounds into oxides, forexample, 450° C., for a discrete amount of time sufficient for theconversion process, for example, thirty minutes. In this example, aceria layer forms on the substrate. Optionally, the process can berepeated as many times as desired, forming a thicker coating of ceria onthe substrate. In some embodiments, the component can be cooled relativeto ambient temperature, such as, for example, to liquid nitrogentemperature, to aid the deposition process. In other embodiments, areducing atmosphere may be used to convert at least a portion of themetal oxides to metal.

In other embodiments, the substrate can comprise one or more polymers,such as polyvinyl chloride. The polymer substrate can be kept at lowertemperatures sufficient to prevent the degradation of the substrateduring the heating process, for example, at liquid nitrogen temperatureswhile the metal compound converts to the oxide due to any technique thatheats the metal compound but not the substrate to a significant degree.Examples of such heating techniques include flash lamps, lasers, andmicrowave heating. In addition, materials that would become degraded byexposure to high temperatures can be kept at lower temperatures usingthe same techniques. For example, glasses, low-melting-temperaturemetals, polycarbonates, and similar substrates can be kept cooler whilethe at least one metal compound is converted to at least one metaloxide.

As used herein in reference to process gases used to carry out theprocess of the invention, the term “high temperature” means atemperature sufficiently high to convert the metal compound to metaloxide, generally in the range of about 200° C. to about 1000° C., suchas, for example, about 200° C. to about 400° C., or about 400° C. toabout 500° C., about 500° C. to about 650° C., about 650° C. to about800° C., or about 800° C. to about 1000° C. Process gases at even highertemperatures can be used, so that, when the gas is passed through thefluid transport or processing system during the process of someembodiments of the invention, the temperature of the gas exiting thesystem is within the range given above.

A given embodiment of the invention described herein may involve one ormore of several basic concepts. For example, one concept relates to asurface treatment that generally meets above-described technicalproperties and can be manufactured at a low cost. Another conceptrelates to a method to form an oxide protective film on the surface of ametal. Another concept relates to a two-step process adapted to form aprophylactic layer onto internal surfaces of a fluid transport orprocessing system. Another concept relates to creating thin films ofnanocrystalline zirconia on surfaces to resist fibrous growth of carbonand other elements. Another concept is related to a means to apply aprotective coating to an assembly of various components using a processto heat an enclosed system as a curing method for the coating.

In some embodiments of the invention, an oxidizing coating may be formedon a substrate by applying a liquid metal compound composition to thesubstrate using a dipping process, spraying, vapor deposition, swabbing,brushing, or other known means of applying a liquid to an internalsurface of a pipe, conduit or process equipment. This liquid metalcompound composition comprises at least one rare earth metal salt of acarboxylic acid and at least one transition metal salt of a carboxylicacid, in a solvent, in some embodiments. The surface, once wetted withthe composition is then exposed to a heated environment that willconvert at least some of the metal compounds to metal oxides, therebyforming an oxidizing coating on the substrate.

The metal oxide coatings resulting from the conversion process, such asthin films of nanocrystalline materials, are applied to materialsubstrates to form one or more thin protective layers. Additionalapplications of the metal compounds followed by conversion environmentexposure (e.g., heating the surface through means described above) maybe done to create multiple layers of thin film oxides slacked one onanother.

The process may be used to create a nanocrystalline structure thatcomprises an oxygen containing molecule for chosen applications.Alternately, the resulting nanocrystalline structure may comprise ametal containing compound, a metal, a ceramic, or a cermet.

One benefit to some embodiments of the invention is the ability to applythe metal compound composition to an assembled system and then to flushhigh temperature gases through the system to achieve the conversionprocess, resulting in a well-dispersed metal oxide coating on allinterior surfaces. This is especially beneficial for welded pipingsystems, heat exchangers, and similar components which use welding fortheir assembly, said welding typically destroying whatever surfacetreatments were applied to the pipes, heat exchangers, or other partsprior to welding. The high temperature conditions of the welding processtend to destroy all protective coatings. The invention provides a way tocreate a final metal oxide coating covering all parts of the processsystem, creating a protective coating for weld joints and componentinteriors alike.

To create a less porous thin film, for some embodiments, material may beadded to the base fluid to act as filler material. In this way, theporosity of the finished coating is altered through the inclusion ofnanoparticles of chosen elements in the liquid metal compoundcomposition prior to the exposure of the composition to an environmentthat will convert at least a portion of the metal compound(s) into metaloxides. The result is a more dense thin film.

In some applications, where it is desirable to reduce a metal oxide to apure metal, the treated substrate may be exposed to a reducing agent,such as hydrogen or other known reducing agent using known means foroxide reduction. For example, 7% hydrogen in argon heated to 350° C. canbe used to form platinum in certain embodiments. Other metals that maybe desired, such as for catalytic purposes, for example, include but arenot limited to platinum, palladium, rhodium, nickel, cerium, gold,silver, zinc, lead, rhenium, ruthenium, and combinations of two or morethereof.

INDUSTRIAL APPLICABILITY

As described above, the method of the invention may be used to provideprophylactic coatings to internal surfaces of fluid transport orprocessing systems, and has particular utility in the area of fluidtransport or processing systems in the petroleum and natural gasindustries, where carbon fouling, corrosion, and hydrogen embrittlementare particular problems in pipelines and processing equipment. Forexample, coating with the ceria, or yttria-stabilized zirconia, or acombination of ceria and zirconia will significantly reduce carbonfouling on steel surfaces exposed to petroleum or other hydrocarbons attemperatures of around 570° C., in effect providing protection againstany effective or measurable carbon deposition. Uncoated steel surfacesexposed to similar conditions become sufficiently fouled with carbon asto require cleaning after about 18 months of service. Inhibition ofcarbon fouling occurs during exposure to petroleum or other hydrocarbonsat temperatures as high as 900° C. Similar improvement in fouling willoccur in fluid processing systems used to process natural gas.

In addition to protection against carbon fouling, the method of theinvention provides protection against other fouling and corrosionproblems often encountered in chemical or hydrocarbon processingoperations in various embodiments. For example, the method of theinvention provides a partial or full barrier against the intrusion ofhydrogen into a metal substrate, reducing surface and substratedegradation through this known mechanism, in some embodiments. Inparticular, the method of the invention provides an effective barrieragainst corrosive attack in further embodiments. Because the resultingsurface coating provides an effective barrier between the material ofthe process equipment (typically metal, such as iron or steel) and theenvironment (e.g., a crude oil, cracked hydrocarbon, or natural gasstream), electrochemical and other reactions between the metal and theprocess stream are effectively reduced or prevented in still otherembodiments. This is particularly important for stainless steel pipingsystems, where the high temperatures involved in welding of the steelcauses chromium (the primary passivating element in stainless steel) tomigrate to grain boundaries, creating a galvanic couple between high Crand low Cr areas, which can lead to corrosive attack. Because the methodof the invention allows application of the coating after the welds havebeen formed (and any high temperature damage has occurred) in someembodiments, areas of the system adjacent to the weld are insulated fromexposure to the potentially corrosive environment of the fluid beingprocessed.

Exposure to certain types of welding, galvanic corrosion, and moreimportantly hydrogen sulfide (often found in petroleum and natural gasprocess streams) can introduce hydrogen into the crystal lattice of themetal process equipment, leading to embrittlement and cracking. Themethod of the invention, by preventing exposure of the metal to anyhydrogen or hydrogen sulfide contained in the process stream, can reduceor eliminate this form of attack in certain embodiments of the presentinvention.

Other systems can be protected from various forms of fouling as well.The heat exchangers that can be protected according to variousembodiments of the present invention include any kind of heat exchanger.Known heat exchangers pass thermal energy, whether for heating orcooling purposes, for example, between gases, between a gas and aliquid, between liquids, between a liquid and a solid, and between a gasand a solid. Heat exchangers for two-phased, semi-solid, paste andslurry systems are also known. Heat exchangers include, for example, oilrefinery heating units, cooling towers, automobile radiators, HVACsystems such as air conditioners, solar towers, geothermal harvesters,refrigeration units, and the like.

The materials that can be protected from fouling according to thepresent invention include any material that can receive a protectivecoating of a metal oxide. Such materials include, for example, metals,ceramics, glasses, and cermets, as well as composites and polymers thatcan withstand the process conditions for converting the metalcarboxylate into metal oxide. The metals that can be protected include,but are not limited to, substantially pure metals, alloys, and steels,such as, for example, low alloy steels, carbon steels, stainless steels,300 series stainless steel, 400 series stainless steel, nickel basealloys, high-chromium steels, and high-molybdenum steels.

The industrial and commercial products that can be protected accordingto the present invention are not limited. Petroleum refinery;petrochemical processing; petroleum transport and storage such aspipelines, oil tankers, fuel transport vehicles, and gas station fueltanks and pumps; sensors; industrial chemical manufacture, storage, andtransportation; automotive fluid systems including fuel systems,lubrication systems, radiators, air heaters and coolers, break systems,power steering, transmissions, and similar hydraulics systems;aeronautical and aerospace fluid storage and transport systems includingfuel systems and hydraulic systems; and food and dairy processingsystems; combustion engines, turbine engines, and rocket engines; amongmany others, can benefit from the present invention.

EXAMPLES Example 1

Five 2″×2″ coupons of mirror-finish SS304 steel (McMaster-Carr) wereindividually designated “Uncoated,” “Zircon,” “Glass,” “YSZ,” and“Clay.” Those compositions mimic chemically and thermally inertmaterials by the same names known in nature and industry, in aninventive manner. A wide range of similar materials can suggestadditional compositions to be used as embodiments of the presentinvention. The “Uncoated” coupon was given no coating, to function asthe control. Each of the other coupons were coated on one side with thefollowing compositions in accordance with embodiments of the presentinvention:

Zircon: Zirconium 2-ethylhexanoate (28% wt. of the final composition.Alfa-Aesar), silicon 2-ethylhexanoate (33.5% wt., Alfa-Aesar) andchromium 2-ethylhexanoate (1% wt., Alfa-Aesar) were mixed into2-ethylhexanoic acid (37.5% wt., Alfa-Aesar), and the composition wasspin-coated onto the steel substrate.Glass: Silicon 2-ethylhexanoate (74% wt., Alfa-Aesar), sodium2-ethylhexanoate (5.2% wt., Alfa-Aesar), calcium 2-ethylhexanoate (11%wt., Alfa-Aesar), and chromium 2-ethylhexanoate (1.4% wt., Alfa-Aesar)were mixed into 2-ethylhexanoic acid (8.4% wt., Alfa-Aesar), and thecomposition was spin-coated onto the steel substrate.YSZ: Yttrium 2-ethylhexanoate powder (2.4% wt., Alfa-Aesar) wasdissolved into 2-ethylhexanoic acid (60% wt., Alfa-Aesar) with stirringat 75-80° C. for one hour. Once the composition was cooled to roomtemperature, zirconium 2-ethylhexanoate (36.6% wt., Alfa-Aesar) andchromium 2-ethylhexanoate (1% wt., Alfa-Aesar) were mixed in. Thecomposition was spin-coated onto the steel substrate.Clay: Aluminum 2-ethylhexanoate (15% wt., Alfa-Aesar), silicon2-ethylhexanoate (45% wt., Alfa-Aesar), and chromium 2-ethylhexanoate(2% wt., Alfa-Aesar) were mixed into 2-ethylhexanoic acid. Thiscomposition was handbrushed onto the substrate, due to the viscosity ofthe composition. The composition apparently reacted with moisture in theair and began to solidify, making application difficult.

The coated steel coupons were placed in a vacuum oven, and evacuated toabout 20-60 millitorr. The coupons were heated to 450° C., and thenallowed to cool to room temperature. The process of depositing andheating was repeated to apply eight coatings of the appropriatecomposition on each coupon.

Each coated coupon was assembled into a test cell having a glasscylinder (1″ inner diameter×1.125″ tall) clamped to the coated portionof the coupon. A rubber gasket formed a seal between the glass cylinderand the coupon. Aqua Regia was prepared from HNO₃ (1 part, by vol., 70%,stock #33260, Alfa-Aesar) and HCl (3 parts, by vol., ˜37%, stock #33257,Alfa-Aesar), poured into the glass cylinder, and allowed to contact thecoupon for one hour. Then, the coupon was removed, rinsed, andphotographed. The photographs of the tested coupons appear in FIGS. 2-6.

Aqua Regia, so-called because it is known to dissolve noble metals suchas gold and platinum, severely etched the Uncoated stainless steelcoupon. See FIG. 2. The Zircon coupon, in contrast, remains largelyunetched, showing only small spots. See FIG. 3. The Glass coupon alsoremains largely unetched, showing feint scratch-like features. See FIG.4. The YSZ coupon shows significant etching. See FIG. 5. The Clay couponalso shows etching, although less severe than the Uncoated coupon. SeeFIG. 6.

On a scale of 0-10, with 0 representing severe etching and 10representing complete protection, the coatings exhibited the followingperformance:

Coupon Performance Uncoated 0 Zircon 8 Glass 7-8 YSZ 0-1 Clay 0-1

Observation of the Zircon and Glass coupons at magnifications of 100× to1,000×before exposure to Aqua Regia revealed uniform, non-porous, mostlyamorphous coatings. Observation of the YSZ coupon at those samemagnifications revealed a surface coating having a crystallinestructure. Observation of the Clay coupon revealed uneven coverage,likely due to the humidity-catalyzed reaction and prematuresolidification. Preparation and application of the Clay composition in amoisture and/or oxygen-free environment may improve the Clay coating'scharacteristics and performance.

These results demonstrate protection of a steel substrate in ahighly-corrosive environment by coatings prepared in accordance with thepresent invention. These results also demonstrate easy experiments fortesting metal oxide coatings to assess how they might perform in a givenenvironment.

Similar experiments can be done in other environments to determine howmetal oxide coatings might perform in those environments. The skilledartisan will recognize that compositions that did not perform wellagainst Aqua Regia may perform well in other environments. For example,the YSZ coating may reduce or prevent coke buildup. Furthermore, acomposition's performance depends in part on the application andconversion conditions. For example, the Clay composition is expected toperform well if it is applied and converted in a suitable environment,as discussed above.

Example 2

FIG. 7 shows a TEM micrograph at 10,000× magnification of a stainlesssteel SS304 substrate (104) having eight coats of an yttria/zirconiacomposition (102). The figure illustrates a diffused coating, labeledOxide-To-Substrate Interlayer (106). In this example, the diffusedcoating is about 10 nm thick. The TEM also shows crystal planes,indicating the nanocrystalline nature of the yttria/zirconia.

Example 3

The interior oil-contacting surfaces of a boiler for a petroleumfractional distillation column are cleaned and then flushed with awell-stirred room temperature composition containing cerium(III)2-ethylhexanoate (203 g; all weights are per kilogram of finalcomposition), chromium(III) acetylacetonate (10.1 g), and cerium(IV)oxide nanoparticles (10.0 g, 10-20 nm, Aldrich) in 2-ethylhexanoic acid(777 g), and the composition is drained from the boiler. Steam at 500°C. heats the boiler in the usual manner for 30 minutes, and then theboiler is allowed to cool. A substantially non-porous cerium oxidecoating stabilized by chromium oxide forms on the oil-contactingsurfaces of the boiler.

Example 4

Under an ethanol-saturated nitrogen atmosphere, the cleanedmilk-contacting surfaces of a milk pasteurizer are flushed with awell-stirred composition containing titanium(IV) ethoxide in ethanol(500 g, 20% Ti, Aldrich) and dry ethanol (500 g), and the composition isdrained. Dry nitrogen heated to 450° C. flushes through the pasteurizerfor fifteen minutes, and the pasteurizer is allowed to cool under a flowof room-temperature nitrogen. Analysis will reveal a titanium dioxidecoating on the milk-contacting surfaces of the pasteurizer.

Example 5

A clean automobile exhaust manifold is dipped in a stirred bathcontaining a first composition that contains zirconium(IV)2,2,6,6-tetramethyl-3,5-heptanedionate (459 g), yttrium(III)2,2,6,6-tetramethyl-3,5-heptanedionate (72.9 g), and hexanes (to 1 kg)so the composition contacts interior and exterior surfaces. Optionally,openings can be plugged so the first composition does not contact theinterior surfaces. The manifold is removed from the composition,suspended, and rotated to allow excess composition to drip into thebath. Microwave radiation irradiates exterior surfaces for ten minutes,and an yttria-stabilized zirconia coating forms on the exterior of themanifold. The exhaust-contacting surfaces of the manifold are flushedwith a second composition containing zirconium(IV)2,2,6,6-tetramethyl-3,5-heptanedionate (459 g), yttrium(III)2,2,6,6-tetramethyl-3,5-heptanedionate (72.9 g), platinum(II)acetylacetonate (1.01 g), and hexanes (to 1 kg), and the composition isdrained from the manifold. Argon gas heated to 450° C. is passed throughthe interior of the manifold for 30 minutes. Then, argon gas containing7% hydrogen heated to 350° C. passes through the interior of themanifold for 30 minutes. An yttria-stabilized zirconia coating will formon the interior surface of the manifold. The interior surface also willcontain platinum metal sites to catalyze the oxidation ofpartially-combusted hydrocarbon fuel. Moreover, an yttria-stabilizedzirconia coating will form to protect the exterior of the manifold fromcorrosion. Optionally, the manifold can be cooled to room temperatureand then slowly lowered into a liquid nitrogen bath for a time.

As previously stated, detailed embodiments of the present invention aredisclosed herein; however, it is to be understood that the disclosedembodiments are merely exemplary of the invention that may be embodiedin various forms. It will be appreciated that many modifications andother variations that will be appreciated by those skilled in the artare within the intended scope of this invention as claimed below withoutdeparting from the teachings, spirit, and intended scope of theinvention. Furthermore, the foregoing description of various embodimentsdoes not necessarily imply exclusion. For example, “some” embodimentsmay include all or part of “other” and “further” embodiments within thescope of this invention.

1. A method for forming at least one metal oxide on a surface of a fluidprocessing or transport system, or a component thereof, comprising: atleast partially assembling the system; applying at least one metalcompound to the surface; exposing the surface with the applied at leastone metal compound to an environment that will convert at least some ofthe compound to at least one metal oxide.
 2. The method of claim 1wherein the at least one metal compound comprises at least one metalcarboxylate, at least one metal alkoxide, at least one metalβ-diketonate, or a combination of any of the foregoing.
 3. The method ofclaim 1, wherein the at least one metal oxide is etched, polished,carburized, nitrided, painted, powder coated, plated, anodized, has oneor more elements deposited alone or in combination, or is subjected tomore than one of the foregoing.
 4. The method of claim 1, wherein thesurface is subjected to at least one thermal treatment, before, after,or both before and after exposing the surface with the applied at leastone metal compound.
 5. A method for decreasing or preventing fouling ona surface of a fluid processing or transport system, or a componentthereof, comprising: applying at least one metal compound to thesurface; and exposing the surface with the applied at least one metalcompound to an environment that will convert at least some of thecompound to at least one metal oxide; wherein the at least one metaloxide is resistant to fouling.
 6. The method of claim 5, wherein the atleast one metal compound comprises at least one metal carboxylate, atleast one metal alkoxide, at least one metal β-diketonate, or acombination of any of the foregoing.
 7. The method of claim 5, whereinthe at least one metal oxide comprises at least one metal oxide chosenfrom the oxides of: Lithium, Beryllium, Sodium, Magnesium, Silicon,Potassium, Calcium, Gallium, Germanium, Arsenic, Bromine, Rubidium,Strontium, Technetium, Ruthenium, Rhodium, Palladium, Indium, Tin,Antimony, Tellurium, Cesium, Barium, Tantalum, Tungsten, Rhenium,Osmium, Iridium, Gold, Mercury, Thallium, Lead, Bismuth, Radium,Actinium, Thorium, Protactinium, Uranium, Neptunium, Plutonium,Americium, Curium, Berkelium, Californium, Einsteinium, Fermium,Mendelevium, Nobelium, Lawrencium, and combinations thereof.
 8. Themethod of claim 5, wherein the at least one metal oxide comprises atleast one metal oxide chosen from the oxides of: Aluminum, Scandium,Titanium, Vanadium, Chromium, Manganese, Iron, Cobalt, Nickel, Copper,Zinc, Yttrium, Zirconium, Niobium, Molybdenum, Silver, Cadmium,Lanthanum, Cerium, Praseodymium, Neodymium, Promethium, Samarium,Europium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium,Ytterbium, Lutetium, Hafnium, Platinum, and combinations thereof.
 9. Themethod of claim 5, wherein the at least one metal compound is present ina metal compound composition that further comprises at least onenanoparticle.
 10. The method of claim 9, wherein the at least onenanoparticle is chosen from Al₂O₃, CeO₂, Ce₂O₃, TiO₂, ZrO₂, andcombinations of two or more of the foregoing.
 11. The method of claim 5,further comprising pretreating the surface before applying the at leastone metal compound.
 12. A method for decreasing or preventing fouling ofa surface of a sensor, or a component thereof, comprising: applying atleast one metal compound to the surface; and exposing the surface withthe applied at least one metal compound to an environment that willconvert at least some of the compound to at least one metal oxide;wherein the at least one metal oxide is resistant to fouling.
 13. Amethod of reducing or preventing coke buildup on a surface of a fluidprocessing or transport system, or a component thereof, comprising:applying at least one metal compound to the surface; and exposing thesurface with the applied at least one metal compound to an environmentthat will convert at least some of the compound to at least one metaloxide; wherein the at least one metal oxide is resistant to cokebuildup.
 14. A method for reducing or preventing corrosive attack on asurface of a fluid processing or transport system, or a componentthereof, comprising: applying at least one metal compound to thesurface; and exposing the surface with the applied at least one metalcompound to an environment that will convert at least some of thecompound to at least one metal oxide; wherein the at least one metaloxide is resistant to corrosive attack.
 15. A method for reducing orpreventing combustion buildup on a flame-heated surface of a fluidprocessing or transport system, or a component thereof, comprising:applying at least one metal compound to the surface; and exposing thesurface with the applied at least one metal compound to an environmentthat will convert at least some of the compound to at least one metaloxide; wherein the at least one metal oxide is resistant to combustionbuildup.
 16. A method for reducing or preventing fouling of at least onemetal surface of a combustion engine system or a component thereof,comprising: applying at least one metal compound to the surface; andexposing the surface with the applied at least one metal compound to anenvironment that will convert at least some of the compound to at leastone metal oxide; wherein the at least one metal oxide is resistant tofouling.
 17. An article of manufacture adaptable to provide a surface ofa fluid processing or transport system, or a component thereof, whereinthe surface comprises: at least one metal oxide, wherein at least someof the at least one metal oxide is present in a diffused coating. 18.The article of claim 17, wherein the surface is an interior surface of afluid processing or transport system or a component thereof.
 19. Thearticle of claim 17, wherein the surface comprises at least part of ahydrocarbon-contacting surface of an oil refining system.
 20. Thearticle of claim 17, wherein the article provides at least part of aheat exchanger.
 21. The article of claim 17, wherein the thin filmcomprises more than one layer.
 22. The article of claim 17, wherein atleast some of the at least one metal oxide is present in an oxidizingcoating.
 23. The article of claim 17, wherein at least some of the atleast one metal oxide is present in a thin layer of a nanocrystallinecoating.
 24. The article of claim 17, wherein the at least one metaloxide comprises: at least one rare earth metal oxide, and at least onetransition metal oxide.
 25. The article of claim 17, wherein the surfacecomprises at least two rare earth metal oxides.
 26. The article of claim17, wherein the surface comprises ceria.
 27. The article of claim 17,wherein the surface comprises yttria and zirconia.
 28. The article ofclaim 17, wherein the surface comprises ceria and zirconia.
 29. Thearticle of claim 17, wherein the surface comprises yttria, zirconia,alumina, or a combination of two or more of the foregoing.
 30. Thearticle of claim 17, wherein the at least one metal oxide is chosen fromZrO₂, CeO₂, Y₂O₃, TiO₂, Fe₂O₃, NiO, Al₂O₃, Cr₂O₃, Mo₂O₃, HfO₂, La₂O₃,Pr₂O₃, Nd₂O₃, Sm₂O₃, Eu₂O₃, Gd₂O₃, Tb₂O₃, Dy₂O₃, Ho₂O₃, Er₂O₃, Tm₂O₃,Yb₂O₃, Lu₂O₃, and combinations of two or more of the foregoing.
 31. Thearticle of claim 17, wherein the surface comprises platinum, palladium,rhodium, nickel, cerium, gold, silver, zinc, lead, rhenium, ruthenium,chrome, tin, or a combination of two or more of the foregoing.